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  • richardmitnick 1:52 pm on March 20, 2019 Permalink | Reply
    Tags: A particularly interesting property of the studied crystals is that they can produce an electrical current of a fixed strength when you shine a light on them, , , In this new work we are essentially proving that this is a new state of quantum matter, LBNL, Topological chiral crystals, Topological materials – which exhibit exotic defect-resistant properties, Topologically protected means that some of the material’s properties are reliably constant even if the material is not perfect   

    From Lawrence Berkeley National Lab: “The Best Topological Conductor Yet: Spiraling Crystal Is the Key to Exotic Discovery” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 20, 2019
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    This animation shows how Fermi arc states form a spiraling structure in a crystal material that serves as a topological conductor. (Credit: Hasan Lab/Princeton University)


    The realization of so-called topological materials – which exhibit exotic, defect-resistant properties and are expected to have applications in electronics, optics, quantum computing, and other fields – has opened up a new realm in materials discovery.

    Several of the hotly studied topological materials to date are known as topological insulators. Their surfaces are expected to conduct electricity with very little resistance, somewhat akin to superconductors but without the need for incredibly chilly temperatures, while their interiors – the so-called “bulk” of the material – do not conduct current.

    Now, a team of researchers working at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered the strongest topological conductor yet, in the form of thin crystal samples that have a spiral-staircase structure. The team’s study of crystals, dubbed topological chiral crystals, is reported in the March 20 edition of the journal Nature.

    2
    The spiraling, chiral structure of crystals containing rhodium and silicon. (Credit: Hasan Lab/Princeton University)

    The DNA-like spiraling structure, or helicoid, in the crystal sample that was the focus of the latest study exhibits a chirality or “handedness” – as a person can be either left-handed or right-handed, and the left hand is a mirror image of the right hand. Chiral properties in some cases can be flipped, like a left-handed person becoming a right-handed person.

    “In this new work we are essentially proving that this is a new state of quantum matter, which is also exhibiting nearly ideal topological surface properties that emerge as a consequence of the chirality of crystal structure,” said M. Zahid Hasan, a topological materials pioneer who led the materials theory and experiments as a visiting faculty scientist in the Materials Sciences Division at Berkeley Lab. Hasan is also the Eugene Higgins Professor of Physics at Princeton University.

    A property that defines topological conductivity – which is related to the electrical conductivity of the material’s surface – was measured to be about 100 times larger than that observed in previously identified topological metals.

    This property, known as the surface Fermi arc, was revealed in X-ray experiments at Berkeley Lab’s Advanced Light Source (ALS) using a technique known as photoemission spectroscopy. The ALS is a synchrotron that produces intense light – from infrared to high-energy X-rays – for dozens of simultaneous experiments.

    LBNL ALS

    Topology is a well-established mathematical concept that relates to the preservation of an object’s geometrical properties even if an object is stretched or deformed in other ways. Some of its experimental applications in 3D electronic materials – such as discovering topological behaviors in materials’ electronic structures – were only realized just over a decade ago, with early and continuing contributions by Berkeley Lab.

    “After more than 12 years of research in topological physics and materials, I do believe that this is only the tip of the iceberg,” Hasan added. “Based on our measurements, this is the most robust, topologically protected conductor metal that anybody has discovered – it is taking us to a new frontier.”

    Topologically protected means that some of the material’s properties are reliably constant even if the material is not perfect. That quality also bolsters the future possibility of practical applications and manufacturability for these types of materials.

    Ilya Belopolski, a Princeton researcher who participated in both the theory and experimental work, noted that a particularly interesting property of the studied crystals – which included cobalt-silicon and rhodium-silicon crystals – is that they can produce an electrical current of a fixed strength when you shine a light on them.

    “Our previous theories showed that – based on the material’s electronic properties that we have now observed – the current would be fixed at specific values,” he said. “It doesn’t matter how big the sample is, or if it’s dirty. It is a universal value. That’s amazing. For applications, the performance will be the same.”

    4
    Princeton University Professor Zahid Hasan, right, describes the exotic behavior of electrons in topological crystals that were studied at Berkeley Lab. Members of Hasan’s research team observe, including: Daniel S. Sanchez (left), Ilya Belopolski (standing, middle), and Tyler A. Cochran (seated, middle). (Credit: Marilyn Chung/Berkeley Lab)

    In previous experiments at the ALS, Hasan’s team had revealed the existence of a type of massless quasiparticles known as Weyl fermions, which had only been known to exist in theory for about 85 years.

    The Weyl fermions, which were observed in synthetic crystals of a semimetal called tantalum arsenide, exhibit some similar electronic properties to those found in the crystals used in the latest study, but lacked their chiral traits. Semimetals are materials that have some metal and some non-metal properties.

    “Our earlier work on Weyl semimetals paved the path for research on exotic topological conductors,” said Hasan. In an November 2017 study that focused on theory surrounding these exotic materials, Hasan’s team predicted that electrons in rhodium-silicon and many related materials behaved in highly unusual ways.

    The team had predicted that quasiparticles in the material – described by the collective motion of electrons – emerge like massless electrons and should behave like slowed, 3D particles of light, with definite handedness or chirality traits unlike in topological insulators or graphene.

    Also, their calculations, published Oct. 1, 2018 in the Nature Materials journal, suggested that electrons in the crystals would collectively behave as if they are magnetic monopoles in their motion. Magnetic monopoles are hypothetical particles with a single magnetic pole – like the Earth without a South Pole that can move independent of a North Pole.

    4
    A simulation showing the spiral structure of Fermi arc properties across different layers of cobalt-silicon crystal samples. (Credit: Hasan Lab/Princeton University)

    All of this unusual topological behavior points back toward the chiral nature of the crystal samples, which create a spiral or “helicoidal” electronic structure, as observed in the experiments, Hasan noted.

    The studied samples, which contain crystals measuring up to a couple of millimeters across, were prepared in advance by several international sources. The crystals were characterized by Hasan’s group at Princeton’s Laboratory for Topological Quantum Matter and Advanced Spectroscopy using a low-temperature scanning tunneling microscope that can scan samples at the atomic scale, and the samples were then transported to Berkeley Lab.

    Prior to study at the ALS, the samples underwent a specialized polishing treatment at Berkeley Lab’s Molecular Foundry, a nanoscale science research facility.

    LBNL Molecular Foundry

    Daniel Sanchez and Tyler Cochran, Princeton researchers who contributed to the study, said that samples for such studies are typically “cleaved,” or broken so that they are atomically flat.

    But in this case, the crystal bonds were very strong because the crystals have a cubic shape. So team members worked with staff at the Molecular Foundry to shoot high-energy argon atoms at the crystal samples to clean and flatten them, and then recrystallized and polished the samples through a heating process.

    The researchers used two different X-ray beamlines at the ALS (Beamline 10.0.1 and Beamline 4.0.3) to uncover the unusual electronic and spin properties of the crystal samples.

    Because the electronic behavior in the samples seems to mimic the chirality in the structure of the crystals, Hasan said there are many other avenues to explore, such as testing whether superconductivity can be transferred across other materials to the topological conductor.

    “This could lead to a new type of superconductor,” he said, “or the exploration of a new quantum effect. Is it possible to have a chiral topological superconductor?”

    Also, while the topological properties observed in rhodium-silicon and cobalt-silicon crystals in the latest study are considered ideal, there are many other materials that have been identified that could be studied to gauge their potential for improved performance for real-world applications, Hasan said.

    “It turns out the same physics might also be possible to realize in other compounds in the future that are more suitable for devices,” he said.

    “It is an immense satisfaction when you predict something exotic and it also appears in the laboratory experiments,” Hasan added, noting his team’s prior successes in predicting the topological properties of materials. “With definitive theoretical predictions, we have combined theory and experiments to advance the knowledge frontier.”

    The Advanced Light Source and Molecular Foundry are DOE Office of Science User Facilities.

    Researchers from Rigetti Quantum Computing; Louisiana State University; Peking University, the Collaborative Innovation Center of Quantum Matter, and the University of Chinese Academy of Science in China; the Max Planck Institute for Chemical Physics of Solids in Germany; and Academia Sinica and National Cheng Kung University in Taiwan also participated in this study.

    This work was supported by the U.S. Department of Energy’s Office of Science, the National Natural Science Foundation of China, the National Key R&D Program of China, the Key Research Program of the Chinese Academy of Science, Academia Sinica’s Innovative Materials and Analysis Technology Exploration program, the Ministry of Science and Technology in Taiwan’s Young Scholar Fellowship Program, National Cheng Kung University in Taiwan, the National Center for Theoretical Sciences in Taiwan, the ERC Advanced Grant, and the UC Berkeley Miller Institute of Basic Research in Science’s Visiting Miller Professorship.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 12:27 pm on March 8, 2019 Permalink | Reply
    Tags: "Scientists Take a Deep Dive Into the Imperfect World of 2D Materials", (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales was used, A form of AFM (atomic force microscopy) was used to view structural details approaching the atomic scale, Adam Schwartzberg: “Now that we know what defects we have and what effect they have on the properties of the material we can use this information to reduce or eliminate defects, , “It’s a very big advance to get this electronic structure on small length scales” said Eli Rotenberg, Because research of WS2 and related 2D materials is still in its infancy there are many unknowns about the roles specific types of defects play in these materials, For this study the defects were due to the sample-growth process, LBNL, , Most of the experiments focused on a single flake of tungsten disulfide, NanoARPES which researchers enlisted to probe the 2D samples with X-rays was used in this work, , Researchers from the Berkeley Lab Chemical Sciences Division Aarhus University in Denmark and Montana State University also participated in this study., Researchers hope to control the amount and kinds of atoms that are affected and the locations where these defects are concentrated in the flakes., The defects were largely concentrated around the edges of the flakes a signature of the growth process, The sample used in the study contained microscopic roughly triangular flakes each measuring about 1 to 5 microns (millionths of a meter) across, The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales, The various techniques were applied at the Molecular Foundry where the material was synthesized and at the ALS, The X-rays knocked out electrons in the sample allowing researchers to measure their direction and energy, These 2D materials could also be incorporated in new forms of memory storage and data transfer such as spintronics and valleytronics, They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, This revealed nanoscale defects and how the electrons interact with each other.,   

    From Lawrence Berkeley National Lab: “Scientists Take a Deep Dive Into the Imperfect World of 2D Materials” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 8, 2019

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Berkeley Lab-led team combines several nanoscale techniques to gain new insights on the effects of defects in a well-studied monolayer material.

    1
    This animation displays a scan of arrow-shaped flakes of a 2D material. Samples were scanned across their electron energy, momentum, and horizontal and vertical coordinates using an X-ray-based technique known as nanoARPES at Berkeley Lab’s Advanced Light Source. Red represents the highest intensity measured, followed by orange, yellow, green, and blue, and purple (least intense). (Credit: Roland Koch/Berkeley Lab)

    Nothing is perfect, or so the saying goes, and that’s not always a bad thing. In a study at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), scientists learned how nanoscale defects can enhance the properties of an ultrathin, so-called 2D material.

    They combined a toolbox of techniques to home in on natural, nanoscale defects formed in the manufacture of tiny flakes of a monolayer material known as tungsten disulfide (WS2) and measured their electronic effects in detail not possible before.

    “Usually we say that defects are bad for a material,” said Christoph Kastl, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry and the lead author of the study, published in the journal ACS Nano. “Here they provide functionality.”

    Tungsten disulfide is a well-studied 2D material that, like other 2D materials of its kind, exhibits special properties because of its atomic thinness. It is particularly well-known for its efficiency in absorbing and emitting light, and it is a semiconductor.

    Members of this family of 2D materials could serve as high-efficiency computer transistors and as other electronics components, and they also are prime candidates for use in ultrathin, high-efficiency solar cells and LED lighting, as well as in quantum computers.

    These 2D materials could also be incorporated in new forms of memory storage and data transfer, such as spintronics and valleytronics, that would revolutionize electronics by making use of materials in new ways to make smaller and more efficient devices.

    The latest result marks the first comprehensive study at the Lab’s Advanced Light Source (ALS) involving a technique called nanoARPES, which researchers enlisted to probe the 2D samples with X-rays.

    LBL ALS

    The X-rays knocked out electrons in the sample, allowing researchers to measure their direction and energy. This revealed nanoscale defects and how the electrons interact with each other.

    The nanoARPES capability is housed in an X-ray beamline, launched in 2016, known as MAESTRO (Microscopic and Electronic Structure Observatory). It is one of dozens of specialized beamlines at the ALS, which produces light in different forms – from infrared to X-rays – for a variety of simultaneous experiments.

    “It’s a very big advance to get this electronic structure on small length scales,” said Eli Rotenberg, a senior staff scientist at the ALS who was a driving force in developing MAESTRO and served as one of the study’s leaders. “That matters for real devices.”

    The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales; a form of AFM (atomic force microscopy) to view structural details approaching the atomic scale; and a combined form of optical spectroscopy (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales.

    The various techniques were applied at the Molecular Foundry, where the material was synthesized, and at the ALS.

    LBNL Molecular Foundry

    The sample used in the study contained microscopic, roughly triangular flakes, each measuring about 1 to 5 microns (millionths of a meter) across. They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, and the defects were largely concentrated around the edges of the flakes, a signature of the growth process. Most of the experiments focused on a single flake of tungsten disulfide.

    2
    This image shows an illustration of the atomic structure of a 2D material called tungsten disulfide. Tungsten atoms are shown in blue and sulfur atoms are shown in yellow. The background image, taken by an electron microscope at Berkeley Lab’s Molecular Foundry, shows groupings of flakes of the material (dark gray) grown by a process called chemical vapor deposition on a titanium dioxide layer (light gray). (Credit: Katherine Cochrane/Berkeley Lab)

    Adam Schwartzberg, a staff scientist at the Molecular Foundry who served as a co-lead in the study, said, “It took a combination of multiple types of techniques to pin down what’s really going on.”

    He added, “Now that we know what defects we have and what effect they have on the properties of the material, we can use this information to reduce or eliminate defects – or if you want the defect, it gives us a way of knowing where the defects are,” and provides fresh insight about how to propagate and amplify the defects in the sample-production process.

    While the concentration of edge defects in the WS2 flakes was generally known before the latest study, Schwartzberg said that their effects on materials performance hadn’t previously been studied in such a comprehensive and detailed way.

    Researchers learned that a 10 percent deficiency in sulfur atoms was associated with the defective edge regions of the samples compared to other regions, and they identified a slighter, 3 percent sulfur deficiency toward the center of the flakes. Researchers also noted a change in the electronic structure and higher abundance of freely moving electrical charge-carriers associated with the high-defect edge areas.

    4
    This sequence of images shows a variety of energy intensities (white and yellow) at the edges of a 2D material known as tungsten disulfide, as measured via different techniques: photoluminescense intensity (far left); contact potential difference map (second from left); exciton emission intensity (third from left) – excitons are pairs consistent of an electrons and their quasiparticle counterpart, called a hole; trion emission intensity (far right) – trions are gropus of three charged quasiparticles consistening of either two electrons and a hole or two holes and an electron). (Credit: Christoph Kastl/Berkeley Lab)

    For this study, the defects were due to the sample-growth process. Future nanoARPES studies will focus on samples with defects that are induced through chemical processing or other treatments. Researchers hope to control the amount and kinds of atoms that are affected, and the locations where these defects are concentrated in the flakes.

    Such tiny tweaks could be important for processes like catalysis, which is used to enhance and accelerate many important industrial chemical production processes, and to explore quantum processes that rely on the production of individual particles that serve as information carriers in electronics.

    Because research of WS2 and related 2D materials is still in its infancy, there are many unknowns about the roles specific types of defects play in these materials, and Rotenberg noted that there is a world of possibilities for so-called “defect engineering” in these materials.

    In addition, MAESTRO’s nanoARPES has the ability to study the electronic structures of stacks of different types of 2D material layers. This can help researchers understand how their properties depend on their physical arrangement, and to explore working devices that incorporate 2D materials.

    “The unprecedented small scale of the measurements – currently approaching 50 nanometers – makes nanoARPES a great discovery tool that will be particularly useful to understand new materials as they are invented,” Rotenberg said.

    MAESTRO is one of the priority beamlines to be upgraded as part of the Lab’s ALS Upgrade (ALS-U) project, a major undertaking that will produce even brighter, more focused beams of light for experiments. “The ALS-U project will further improve the performance of the nanoARPES technique,” Rotenberg said, “making its measurements 10 to 30 times more efficient and significantly improving our ability to reach even shorter length scales.”

    NanoARPES could play an important role in the development of new solar technologies, because it allows researchers to see how nanoscale variations in chemical makeup, number of defects, and other structural features affect the electrons that ultimately govern their performance. These same issues are important for many other complex materials, such as superconductors, magnets, and thermoelectrics – which convert temperature to current and vice versa – so nanoARPES will also be very useful for these as well.

    The Molecular Foundry and ALS are both DOE Office of Science User Facilities.

    Researchers from the Berkeley Lab Chemical Sciences Division, Aarhus University in Denmark, and Montana State University also participated in this study. The work was supported by the U.S. Department of Energy’s Office of Basic Energy Sciences, the DOE Early Career Grant program, Berkeley Lab’s Laboratory Directed Research and Development program, the Villum Foundation, and the German Academic Exchange Service.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 5:32 pm on March 7, 2019 Permalink | Reply
    Tags: a field that could extend the limits of Moore’s law by miniaturizing electronic components, A new study led by Berkeley Lab reveals how aligned layers of atomically thin semiconductors can yield an exotic new quantum material, A team of researchers led by the Department of Energy’s Lawrence Berkeley National Laboratory has developed a method that could turn ordinary semiconducting materials into quantum machines, Aiming Yan and Alex Zettl used a transmission electron microscope (TEM) at Berkeley Lab’s Molecular Foundry to take atomic-resolution images, Also contributing to the study were researchers from Arizona State University and the National Institute for Materials Science in Japan, Also valleytronics, and superconductivity which would allow electrons to flow in devices with virtually no resistance, , “This is an amazing discovery because we didn’t think of these semiconducting materials as strongly interacting” said Feng Wang, LBNL, , The researchers next plan to measure how this new quantum system could be applied to optoelectronics, The TEM images confirmed what they had suspected all along: the materials had indeed formed a moiré superlattice, Two-dimensional (2D) materials which are just one atom thick are like nanosized building blocks that can be stacked arbitrarily to form tiny devices, When the lattices of two 2D materials are similar and well-aligned a repeating pattern called a moiré superlattice can form   

    From Lawrence Berkeley National Lab: “When Semiconductors Stick Together, Materials Go Quantum” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 7, 2019
    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    A new study led by Berkeley Lab reveals how aligned layers of atomically thin semiconductors can yield an exotic new quantum material.

    1
    A method developed by a Berkeley Lab-led research team may one day turn ordinary semiconducting materials into quantum electronic devices. (Credit: iStock.com/NiPlot)

    A team of researchers led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has developed a simple method that could turn ordinary semiconducting materials into quantum machines – superthin devices marked by extraordinary electronic behavior. Such an advancement could help to revolutionize a number of industries aiming for energy-efficient electronic systems – and provide a platform for exotic new physics.

    The study describing the method, which stacks together 2D layers of tungsten disulfide and tungsten diselenide to create an intricately patterned material, or superlattice, was published online recently in the journal Nature.

    “This is an amazing discovery because we didn’t think of these semiconducting materials as strongly interacting,” said Feng Wang, a condensed matter physicist with Berkeley Lab’s Materials Sciences Division and professor of physics at UC Berkeley. “Now this work has brought these seemingly ordinary semiconductors into the quantum materials space.”

    2
    The twist angle formed between atomically thin layers of tungsten disulfide and tungsten diselenide acts as a “tuning knob,” transforming these semiconductors into an exotic quantum material. (Credit: Berkeley Lab) (Credit: Berkeley Lab)

    Two-dimensional (2D) materials, which are just one atom thick, are like nanosized building blocks that can be stacked arbitrarily to form tiny devices. When the lattices of two 2D materials are similar and well-aligned, a repeating pattern called a moiré superlattice can form.

    For the past decade, researchers have been studying ways to combine different 2D materials, often starting with graphene – a material known for its ability to efficiently conduct heat and electricity. Out of this body of work, other researchers had discovered that moiré superlattices formed with graphene exhibit exotic physics such as superconductivity when the layers are aligned at just the right angle.

    The new study, led by Wang, used 2D samples of semiconducting materials – tungsten disulfide and tungsten diselenide – to show that the twist angle between layers provides a “tuning knob” to turn a 2D semiconducting system into an exotic quantum material with highly interacting electrons.

    Entering a new realm of physics

    Co-lead authors Chenhao Jin, a postdoctoral scholar, and Emma Regan, a graduate student researcher, both of whom work under Wang in the Ultrafast Nano-Optics Group at UC Berkeley, fabricated the tungsten disulfide and tungsten diselenide samples using a polymer-based technique to pick up and transfer flakes of the materials, each measuring just tens of microns in diameter, into a stack.

    They had fabricated similar samples of the materials for a previous study [Science], but with the two layers stacked at no particular angle. When they measured the optical absorption of a new tungsten disulfide and tungsten diselenide sample for the current study, they were taken completely by surprise.

    The absorption of visible light in a tungsten disulfide/tungsten diselenide device is largest when the light has the same energy as the system’s exciton, a quasiparticle that consists of an electron bound to a hole that is common in 2D semiconductors. (In physics, a hole is a currently vacant state that an electron could occupy.)

    3
    The large potential energy of three distinct exciton states in a 2D tungsten disulfide/tungsten diselenide device could introduce exotic quantum phenomena into semiconducting materials. (Credit: Berkeley Lab)

    For light in the energy range that the researchers were considering, they expected to see one peak in the signal that corresponded to the energy of an exciton.

    Instead, they found that the original peak that they expected to see had split into three different peaks representing three distinct exciton states.

    What could have increased the number of exciton states in the tungsten disulfide/tungsten diselenide device from one to three? Was it the addition of a moiré superlattice?

    To find out, their collaborators Aiming Yan and Alex Zettl used a transmission electron microscope (TEM) at Berkeley Lab’s Molecular Foundry, a nanoscale science research facility, to take atomic-resolution images of the tungsten disulfide/tungsten diselenide device to check how the materials’ lattices were aligned.

    The TEM images confirmed what they had suspected all along: the materials had indeed formed a moiré superlattice. “We saw beautiful, repeating patterns over the entire sample,” said Regan. “After comparing this experimental observation with a theoretical model, we found that the moiré pattern introduces a large potential energy periodically over the device and could therefore introduce exotic quantum phenomena.”

    The researchers next plan to measure how this new quantum system could be applied to optoelectronics, which relates to the use of light in electronics; valleytronics, a field that could extend the limits of Moore’s law by miniaturizing electronic components; and superconductivity, which would allow electrons to flow in devices with virtually no resistance.

    Also contributing to the study were researchers from Arizona State University and the National Institute for Materials Science in Japan.

    The work was supported by the DOE Office of Science. Additional funding was provided by the National Science Foundation, the Department of Defense, and the Elemental Strategy Initiative conducted by MEXT, Japan, and JSPS KAKENHI. The Molecular Foundry is a DOE Office of Science user facility.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 3:59 pm on March 4, 2019 Permalink | Reply
    Tags: A nanoworld on a chip, , “Ice rules” a principle that governs how atoms arrange themselves in ice formed from water or the mineral pyrochlore, , Berkeley Lab-led study could lead to smaller memory devices microelectronics and spintronics, LBNL, , , PEEM-X-ray photoemission electron microscopy   

    From Lawrence Berkeley National Lab: “How to Catch a Magnetic Monopole in the Act” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 4, 2019
    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    Berkeley Lab-led study could lead to smaller memory devices, microelectronics, and spintronics

    1
    Magnetic monopoles in motion at 210 K. Red dots represent positive magnetic charges (north poles), while blue dots represent negative magnetic charges (south poles). (Credit: Farhan/Berkeley Lab)

    A research team led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created a nanoscale “playground” on a chip that simulates the formation of exotic magnetic particles called monopoles. The study – published recently in Science Advances – could unlock the secrets to ever-smaller, more powerful memory devices, microelectronics, and next-generation hard drives that employ the power of magnetic spin to store data.

    Follow the ‘ice rules’

    For years, other researchers have been trying to create a real-world model of a magnetic monopole – a theoretical magnetic, subatomic particle that has a single north or south pole. These elusive particles can be simulated and observed by manufacturing artificial spin ice materials – large arrays of nanomagnets that have structures analogous to water ice – wherein the arrangement of atoms isn’t perfectly symmetrical, leading to residual north or south poles.

    2
    This nanoscale “playground” on a chip uses nanomagnets to simulate the formation of exotic magnetic particles called “monopoles.” (Credit: Farhan/Berkeley Lab)

    Opposites attract in magnetism (north poles are drawn to south poles, and vice-versa) so these single poles attempt to move to find their perfect match. But because conventional artificial spin ices are 2D systems, the monopoles are highly confined, and are therefore not realistic representations of how magnetic monopoles behave, said lead author Alan Farhan, who was a postdoctoral fellow at Berkeley Lab’s Advanced Light Source (ALS) at the time of the study, and is now with the Paul Scherrer Institute in Switzerland.

    LBL ALS

    To overcome this obstacle, the Berkeley Lab-led team simulated a nanoscale 3D system that follows “ice rules,” a principle that governs how atoms arrange themselves in ice formed from water or the mineral pyrochlore.

    “This is a crucial element of our work,” said Farhan. “With our 3D system, a north monopole or south monopole can move wherever it wants to go, interacting with other particles in its environment like an isolated magnetic charge would – in other words, like a monopole.”

    A nanoworld on a chip

    4
    This XMCD (X-ray magnetic circular dichroism) image sequence recorded at 190 K shows how monopoles might form and move in response to changes in temperature. (Credit: Farhan/Berkeley Lab)

    The team used sophisticated lithography tools developed at Berkeley Lab’s Molecular Foundry, a nanoscale science research facility, to pattern a 3D, square lattice of nanomagnets. Each magnet in the lattice is about the size of a bacterium and rests on a flat, 1-by-1-centimeter silicon wafer.

    LBNL Molecular Foundry

    “It’s a nanoworld – with tiny architecture on a tiny wafer,” but atomically configured exactly like natural ice, said Farhan.

    To build the nanostructure, the researchers synthesized two exposures, each one aligned within 20 to 30 nanometers. At the Molecular Foundry, co-author Scott Dhuey fabricated nanopatterns of four types of structures onto a tiny silicon chip. The chips were then studied at the ALS, a synchrotron light source research facility open to visiting scientists from around the world. The researchers used a technique called X-ray photoemission electron microscopy (PEEM), directing powerful beams of X-ray light sensitive to magnetic structures at the nanopatterns to observe how monopoles might form and move in response to changes in temperature.

    In contrast to PEEM microscopes at other light sources, Berkeley Lab’s PEEM3 microscope has a higher X-ray angle of incidence, minimizing shadow effects – which are similar to the shadows cast by a building when the sun strikes the surface at a certain angle. “In fact, the images recorded reveal no shadow effect whatsoever,” said Farhan. “This makes the PEEM3 the most crucial element to this project’s success.”

    Farhan added that the PEEM3 is the only microscope in the world that gives users full temperature control in the sub-100 Kelvin (below minus 280 degrees Fahrenheit) range, capturing in real time how emergent magnetic monopoles form as artificial frozen ice melts into a liquid, and as liquid evaporates into a gas-like state of magnetic charges – a form of matter known as plasma.

    The researchers now hope to pattern smaller and smaller nanomagnets for the advancement of smaller yet more powerful spintronics – a sought-after field of microelectronics that taps into particles’ magnetic spin properties to store more data in smaller devices such as magnetic hard drives.

    Such devices would use magnetic films and superconducting thin films to deploy and manipulate magnetic monopoles to sort and store data based on the north or south direction of their poles – analogous to the ones and zeros in conventional magnetic storage devices.

    The ALS and the Molecular Foundry are DOE Office of Science user facilities.

    The work research was supported by the U.S. Department of Energy’s Office of Science, and the Swiss National Science Foundation.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

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  • richardmitnick 1:47 pm on February 25, 2019 Permalink | Reply
    Tags: "Laser ‘Drill’ Sets a New World Record in Laser-Driven Electron Acceleration", , , , , LBNL,   

    From Lawrence Berkeley National Lab: “Laser ‘Drill’ Sets a New World Record in Laser-Driven Electron Acceleration” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    February 25, 2019
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Scientists working at Berkeley Lab’s BELLA Center nearly double their previous record set in 2014.

    LBNL Bella Center during constructon

    1
    This animation shows a plasma channel’s electron density profile (blue) formed inside a sapphire tube (gray) with the combination of an electrical discharge and an 8-nanosecond laser pulse (red, orange, and yellow). Time is shown in nanoseconds. This plasma channel was used to guide femtoseconds-long “driver” laser pulses from the BELLA petawatt laser system, which generated plasma waves and accelerated electrons to 8 billion electron volts in just 20 centimeters. (Credit: Gennadiy Bagdasarov/Keldysh Institute of Applied Mathematics; Anthony Gonsalves/Berkeley Lab)

    Combining a first laser pulse to heat up and “drill” through a plasma, and another to accelerate electrons to incredibly high energies in just tens of centimeters, scientists have nearly doubled the previous record for laser-driven particle acceleration.

    The laser-plasma experiments, conducted at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), are pushing toward more compact and affordable types of particle acceleration to power exotic, high-energy machines – like X-ray free-electron lasers and particle colliders – that could enable researchers to see more clearly at the scale of molecules, atoms, and even subatomic particles.

    The new record of propelling electrons to 7.8 billion electron volts (7.8 GeV) at the Berkeley Lab Laser Accelerator (BELLA) Center surpasses a 4.25 GeV result at BELLA announced in 2014. The latest research is detailed in the Feb. 25 edition of the journal Physical Review Letters. The record result was achieved during the summer of 2018.

    The experiment used incredibly intense and short “driver” laser pulses, each with a peak power of about 850 trillion watts and confined to a pulse length of about 35 quadrillionths of a second (35 femtoseconds). The peak power is equivalent to lighting up about 8.5 trillion 100-watt lightbulbs simultaneously, though the bulbs would be lit for only tens of femtoseconds.

    Each intense driver laser pulse delivered a heavy “kick” that stirred up a wave inside a plasma – a gas that has been heated enough to create charged particles, including electrons. Electrons rode the crest of the plasma wave, like a surfer riding an ocean wave, to reach record-breaking energies within a 20-centimeter-long sapphire tube.

    “Just creating large plasma waves wasn’t enough,” noted Anthony Gonsalves, the lead author of the latest study. “We also needed to create those waves over the full length of the 20-centimeter tube to accelerate the electrons to such high energy.”

    To do this required a plasma channel, which confines a laser pulse in much the same way that a fiber-optic cable channels light. But unlike a conventional optical fiber, a plasma channel can withstand the ultra-intense laser pulses needed to accelerate electrons. In order to form such a plasma channel, you need to make the plasma less dense in the middle.

    3
    Different generations of sapphire tubes, called capillaries, are pictured here. The tubes are used to generate and confine plasmas, and to accelerate electrons. A 20-centimeter capillary setup, similar to the one used in the latest experiments, is pictured at left. (Credit: Marilyn Chung/Berkeley Lab)

    In the 2014 experiment, an electrical discharge was used to create the plasma channel, but to go to higher energies the researchers needed the plasma’s density profile to be deeper – so it is less dense in the middle of the channel. In previous attempts the laser lost its tight focus and damaged the sapphire tube. Gonsalves noted that even the weaker areas of the laser beam’s focus – its so-called “wings” – were strong enough to destroy the sapphire structure with the previous technique.

    Eric Esarey, BELLA Center Director, said the solution to this problem was inspired by an idea from the 1990s to use a laser pulse to heat the plasma and form a channel. This technique has been used in many experiments, including a 2004 Berkeley Lab effort that produced high-quality beams reaching 100 million electron volts (100 MeV).

    Both the 2004 team and the team involved in the latest effort were led by former ATAP and BELLA Center Director Wim Leemans, who is now at the DESY laboratory in Germany. The researchers realized that combining the two methods – and putting a heater beam down the center of the capillary – further deepens and narrows the plasma channel. This provided a path forward to achieving higher-energy beams.

    In the latest experiment, Gonsalves said, “The electrical discharge gave us exquisite control to optimize the plasma conditions for the heater laser pulse. The timing of the electrical discharge, heater pulse, and driver pulse was critical.”

    4
    This animation shows a 3D rendering of plasma waves (blue) excited by a petawatt laser pulse (red) at Berkeley Lab’s BELLA Center as it propagates in a plasma channel. Some of the background electrons are trapped and accelerated to an energy of up to 7.8 GeV in the plasma wave (pink/purple). The simulation was performed on the Edison supercomputer at Berkeley Lab’s National Energy Research Scientific Computing Center. (Credit: Carlo Benedetti/Berkeley Lab)

    The combined technique radically improved the confinement of the laser beam, preserving the intensity and the focus of the driving laser, and confining its spot size, or diameter, to just tens of millionths of a meter as it moved through the plasma tube. This enabled the use of a lower-density plasma and a longer channel. The previous 4.25 GeV record had used a 9-centimeter channel.

    The team needed new numerical models (codes) to develop the technique. A collaboration including Berkeley Lab, the Keldysh Institute of Applied Mathematics in Russia, and the ELI-Beamlines Project in the Czech Republic adapted and integrated several codes. They combined MARPLE and NPINCH, developed at the Keldysh Institute, to simulate the channel formation; and INF&RNO, developed at the BELLA Center, to model the laser-plasma interactions.

    “These codes helped us to see quickly what makes the biggest difference – what are the things that allow you to achieve guiding and acceleration,” said Carlo Benedetti, the lead developer of INF&RNO. Once the codes were shown to agree with the experimental data, it became easier to interpret the experiments, he noted.

    “Now it’s at the point where the simulations can lead and tell us what to do next,” Gonsalves said.

    Benedetti noted that the heavy computations in the codes drew upon the resources of the National Energy Research Scientific Computing Center (NERSC) at Berkeley Lab.

    NERSC

    NERSC Cray Cori II supercomputer at NERSC at LBNL, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC Hopper Cray XE6 supercomputer


    LBL NERSC Cray XC30 Edison supercomputer


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future work pushing toward higher-energy acceleration could require far more intensive calculations that approach a regime known as exascale computing.

    “Today, the beams produced could enable the production and capture of positrons,” which are electrons’ positively charged counterparts, said Esarey.

    He noted that there is a goal to reach 10 GeV energies in electron acceleration at BELLA, and future experiments will target this threshold and beyond.

    “In the future, multiple high-energy stages of electron acceleration could be coupled together to realize an electron-positron collider to explore fundamental physics with new precision,” he said.

    Also participating in this research were researchers from UC Berkeley and the National Research Nuclear University in Russia.

    This work was supported by the Department of Energy’s Office of Science, the Alexander von Humboldt Foundation, and the National Science Foundation.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

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    DOE Seal

     
  • richardmitnick 12:37 pm on February 21, 2019 Permalink | Reply
    Tags: "Big Data at the Atomic Scale: New Detector Reaches New Frontier in Speed", A new detector that can capture atomic-scale images in millionths-of-a-second increments., , , , known as the “4D Camera” (for Dynamic Diffraction Direct Detector), LBNL, , NCEM-National Center for Electron Microscopy, The Molecular Foundry, The new detector, The Transmission Electron Aberration-corrected Microscope (TEAM 0.5) at Berkeley Lab   

    From Lawrence Berkeley National Lab: “Big Data at the Atomic Scale: New Detector Reaches New Frontier in Speed” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    February 21, 2019
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    The Transmission Electron Aberration-corrected Microscope (TEAM 0.5) at Berkeley Lab has been upgraded with a new detector that can capture atomic-scale images in millionths-of-a-second increments. (Credit: Thor Swift/Berkeley Lab)


    This video provides an overview of the R&D effort to upgrade an electron microscope at Berkeley Lab’s Molecular Foundry with a superfast detector, the 4D Camera. The detector, which is linked to a supercomputer at Berkeley Lab via a high-speed data connection, can capture more images at a faster rate, revealing atomic-scale details across much larger areas than was possible before. (Credit: Marilyn Chung/Berkeley Lab)

    Advances in electron microscopy – using electrons as imaging tools to see things well beyond the reach of conventional microscopes that use light – have opened up a new window into the nanoscale world and brought a wide range of samples into focus as never before.

    Electron microscopy experiments can only use a fraction of the possible information generated as the microscope’s electron beam interacts with samples. Now, a team at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of electron detector that captures all of the information in these interactions.

    This new tool, a superfast detector installed Feb. 12 at Berkeley Lab’s Molecular Foundry, a nanoscale science user facility, captures more images at a faster rate, revealing atomic-scale details across much larger areas than was possible before. The Molecular Foundry and its world-class electron microscopes in the National Center for Electron Microscopy (NCEM) provide access to researchers from around the world.

    Faster imaging can also reveal important changes that samples are undergoing and provide movies vs. isolated snapshots. It could, for example, help scientists to better explore working battery and microchip components at the atomic scale before the onset of damage.

    The detector, which has a special direct connection to the Cori supercomputer at the Lab’s National Energy Research Scientific Computing Center (NERSC), will enable scientists to record atomic-scale images with timing measured in microseconds, or millionths of a second – 100 times faster than possible with existing detectors.

    NERSC Cray Cori II supercomputer at NERSC at LBNL, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    “It is the fastest electron detector ever made,” said Andrew Minor, NCEM facility director at the Molecular Foundry.

    “It opens up a new time regime to explore with high-resolution microscopy. No one has ever taken continuous movies at this time resolution” using electron imaging, he said. “What happens there? There are all kinds of dynamics that might happen. We just don’t know because we’ve never been able to look at them before.” The new movies could reveal tiny deformations and movements in materials, for example, and show chemistry in action.

    The development of the new detector, known as the “4D Camera” (for Dynamic Diffraction Direct Detector), is the latest in a string of pioneering innovations in electron microscopy, atomic-scale imaging, and high-speed data transfer and computing at Berkeley Lab that span several decades.

    “Our group has been working for some time on making better detectors for microscopy,” said Peter Denes, a Berkeley Lab senior scientist and a longtime pioneer in the development of electron microscopy tools.

    “You get a whole scattering pattern instead of just one point, and you can go back and reanalyze the data to find things that maybe you weren’t focusing on before,” Denes said. This quickly produces a complete image of a sample by scanning across it with an electron beam and capturing information based on the electrons that scatter off the sample.

    Mary Scott, a faculty scientist at the Molecular Foundry, said that the unique geometry of the new detector allows studies of both light and heavyweight elements in materials side by side. “The reason you might want to perform one of these more complicated experiments would be to measure the positions of light elements, particularly in materials that might be really sensitive to the electron beam – like lithium in a battery material – and ideally you would be able to also precisely measure the positions of heavy elements in that same material,” she said.

    The new detector has been installed on the Transmission Electron Aberration-corrected Microscope 0.5 (TEAM 0.5) at the Molecular Foundry, which set high-resolution records when it launched at NCEM a decade ago and allows visiting researchers to access single-atom resolution for some samples. The detector will generate a whopping 4 terabytes of data per minute.

    “The amount of data is equivalent to watching about 60,000 HD movies simultaneously,” said Peter Ercius, a staff scientist at the Molecular Foundry who specializes in 3D atomic-scale imaging.

    Brent Draney, a networking architect at Berkeley Lab’s NERSC, said that Ercius and Denes had approached NERSC to see what it would take to build a system that could handle this huge, 400-gigabit stream of data produced by the 4D Camera.

    His response: “We actually already have a system capable of doing that. What we really needed to do is to build a network between the microscope and the supercomputer.”

    2
    A technician works on the TEAM 0.5 microscope. The microscope has been upgraded with a superfast detector called the 4D Camera that can capture atomic-scale images in millionths-of-a-second increments. (Credit: Thor Swift/Berkeley Lab)

    Camera data is transferred over about 100 fiber-optic connections into a high-speed ethernet connection that is about 1,000 times faster than the average home network, said Ian Johnson, a staff scientist in Berkeley Lab’s Engineering Division. The network connects the Foundry to the Cori supercomputer at NERSC.

    Berkeley Lab’s Energy Sciences Network (ESnet), which connects research centers with high-speed data networks, participated in the effort.

    Ercius said, “The supercomputer will analyze the data in about 20 seconds in order to provide rapid feedback to the scientists at the microscope to tell if the experiment was successful or not.”

    Jim Ciston, another Molecular Foundry staff scientist, said, “We’ll actually capture every electron that comes through the sample as it’s scattered. Through this really large data set we’ll be able to perform ‘virtual’ experiments on the sample – we won’t have to go back and take new data from different imaging conditions.”

    The work on the new detector and its supporting data systems should benefit other facilities that produce high volumes of data, such as the Advanced Light Source and its planned upgrade, and the LCLS-II project at SLAC National Accelerator Laboratory, Ciston noted.

    LBNL Advanced Light Source

    SLAC LCLS-II

    The Advanced Light Source, ESnet, Molecular Foundry, and NERSC are DOE Office of Science User Facilities.

    The development of the 4D Camera was supported by the Accelerator and Detector Research Program of the Department of Energy’s Office of Basic Energy Sciences, and work at the Molecular Foundry was supported by the DOE’s Office of Basic Energy Sciences.

    3
    This computer chip is a component in a superfast detector called the 4D Camera. The detector is an upgrade for a powerful electron microscope at Berkeley Lab’s Molecular Foundry. (Credit: Marilyn Chung/Berkeley Lab)

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 3:06 pm on February 5, 2019 Permalink | Reply
    Tags: A way to overcome these hurdles by turning parts of a 13000-mile-long testbed of “dark fiber” unused fiber-optic cable owned by the DOE Energy Sciences Network (ESnet) into a highly sensitive seis, By coupling DAS technology with dark fiber Berkeley Lab researchers were able to detect both local and distant earthquakes from Berkeley to Gilroy California to Chiapas Mexico, LBNL, Only a few seismic sensors have been installed throughout remote areas of California making it hard to understand the impacts of future earthquakes as well as small earthquakes occurring on unmapped f, , Sensors cost tens of thousands of dollars to make and install underground, The current study’s findings also suggest that researchers may no longer have to choose between data quality and cost, With 300 terabytes of raw data collected for the study the researchers have been challenged to find ways to effectively manage and process the “fire hose” of seismic information   

    From Lawrence Berkeley National Lab: “Dark Fiber Lays Groundwork for Long-Distance Earthquake Detection and Groundwater Mapping” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    February 5, 2019

    Berkeley Lab researchers capture a detailed picture of how earthquakes travel through the Earth’s subsurface.

    1
    A research team led by Jonathan Ajo-Franklin of Berkeley Lab’s Earth and Environmental Sciences Area (EESA) is turning parts of a 13,000-mile-long “dark fiber” testbed owned by DOE’s ESnet into a highly sensitive seismic activity sensor. L-R: Inder Monga (ESnet), Verónica Rodríguez Tribaldos (EESA), Jonathan Ajo-Franklin, and Nate Lindsey (EESA).(Credit: Paul Mueller/Berkeley Lab)

    In traditional seismology, researchers studying how the earth moves in the moments before, during, and after an earthquake rely on sensors that cost tens of thousands of dollars to make and install underground. And because of the expense and labor involved, only a few seismic sensors have been installed throughout remote areas of California, making it hard to understand the impacts of future earthquakes as well as small earthquakes occurring on unmapped faults.

    Now researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have figured out a way to overcome these hurdles by turning parts of a 13,000-mile-long testbed of “dark fiber,” unused fiber-optic cable, owned by the DOE Energy Sciences Network (ESnet), into a highly sensitive seismic activity sensor that could potentially augment the performance of earthquake early warning systems currently being developed in the western United States. The study detailing the work – the first to employ a large regional network as an earthquake sensor – was published this week in Nature’s Scientific Reports.

    According to Jonathan Ajo-Franklin, a staff scientist in Berkeley Lab’s Earth and Environmental Sciences Area who led the study, there are approximately 10 million kilometers of fiber-optic cable around the world, and about 10 percent of that consists of dark fiber.

    The Ajo-Franklin group has been working toward this type of experiment for several years. In a 2017 study [Nature Scientific Reports], they installed a fiber-optic cable in a shallow trench in Richmond, California, and demonstrated that a new sensing technology called distributed acoustic sensing (DAS) could be used for imaging of the shallow subsurface. DAS is a technology that measures seismic wavefields by shooting short laser pulses across the length of the fiber. In a follow-up study [Geophysical Rsearch Letters], they and a group of collaborators demonstrated for the first time that fiber-optic cables could be used as sensors for detecting earthquakes.

    2
    A research team led by Berkeley Lab’s Jonathan Ajo-Franklin ran their experiments on a 20-mile segment of the 13,000-mile-long ESnet Dark Fiber Testbed that extends from West Sacramento to Woodland, California. (Credit: Ajo-Franklin/Berkeley Lab)

    The current study uses the same DAS technique, but instead of deploying their own fiber-optic cable, the researchers ran their experiments on a 20-mile segment of the 13,000-mile-long ESnet Dark Fiber Testbed that extends from West Sacramento to Woodland, California. “To further verify our results from the 2017 study, we knew we would need to run the DAS tests on an actual dark fiber network,” said Ajo-Franklin, who also heads Berkeley Lab’s Geophysics Department.

    “When Jonathan approached me about using our Dark Fiber Testbed, I didn’t even know it was possible” to use a network as a sensor, said Inder Monga, Executive Director of ESnet and director of the Scientific Networking Division at Berkeley Lab. “No one had done this work before. But the possibilities were tremendous, so I said, ‘Sure, let’s do this!”

    Chris Tracy from ESnet worked closely with the researchers to figure out the logistics of implementation. Telecommunications company CenturyLink provided fiber installation information.

    Because the ESnet Testbed has regional coverage, the researchers were able to monitor seismic activity and environmental noise with finer detail than previous studies.

    “The coverage of the ESnet Dark Fiber Testbed provided us with subsurface images at a higher resolution and larger scale than would have been possible with a traditional sensor network,” said co-author Verónica Rodríguez Tribaldos, a postdoctoral researcher in Ajo-Franklin’s lab. “Conventional seismic networks often employ only a few dozen sensors spaced apart by several kilometers to cover an area this large, but with the ESnet Testbed and DAS, we have 10,000 sensors in a line with a two-meter spacing. This means that with just one fiber-optic cable you can gather very detailed information about soil structure over several months.”

    3
    By coupling DAS technology with dark fiber, Berkeley Lab researchers were able to detect both local and distant earthquakes, from Berkeley to Gilroy, California, to Chiapas, Mexico. (Credit: Ajo-Franklin/Berkeley Lab)

    After seven months of using DAS to record data through the ESnet Dark Fiber Testbed, the researchers proved that the benefits of using a commercial fiber are manifold. “Just by listening for 40 minutes, this technology has the potential to do about 10 different things at once. We were able to pick up very low frequency waves from distant earthquakes as well as the higher frequencies generated by nearby vehicles,” said Ajo-Franklin. The technology allowed the researchers to tell the difference between a car or moving train versus an earthquake, and to detect both local and distant earthquakes, from Berkeley to Gilroy to Chiapas, Mexico. The technology can also be used to characterize soil quality, provide information on aquifers, and be integrated into geotechnical studies, he added.

    With such a detailed picture of the subsurface, the technology has potential for use in time-lapse studies of soil properties, said Rodríguez Tribaldos. For example, in environmental monitoring, this tool could be used to detect long-term groundwater changes, the melting of permafrost, or the hydrological changes involved in landslide hazards.

    The current study’s findings also suggest that researchers may no longer have to choose between data quality and cost. “Cell phone sensors are inexpensive and tell us when a large earthquake happens nearby, but they will not be able to record the fine vibrations of the planet,” said co-author Nate Lindsey, a UC Berkeley graduate student who led the field work and earthquake analysis for the 2017 study. “In this study, we showed that inexpensive fiber-optics pick up those small ground motions with surprising quality.”

    With 300 terabytes of raw data collected for the study, the researchers have been challenged to find ways to effectively manage and process the “fire hose” of seismic information. Ajo-Franklin expressed hope to one day build a seismology data portal that couples ESnet as a sensor and data transfer mechanism, with analysis and long-term data storage managed by Berkeley Lab’s supercomputing facility, NERSC (National Energy Research Scientific Computing Center).

    Monga added that even though the Dark Fiber Testbed will soon be lit for the next generation of ESnet, dubbed “ESnet 6,” there may be sections that could be used for seismology. “Although it was completely unexpected that ESnet – a transatlantic network dedicated for research – could be used as a seismic sensor, it fits perfectly within our mission,” he said. “At ESnet, we want to enable scientific discovery unconstrained by geography.”

    The research was funded by Laboratory Directed Research and Development Funding with earlier research supported by the Strategic Environmental Research and Defense Program (SERDP), U.S. Department of Defense.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:52 pm on January 17, 2019 Permalink | Reply
    Tags: A next-generation cosmic microwave background experiment known as CMB-S4, LBNL, POLARBEAR-2/Simons Array experiments in Chile, Scientists Team Up With Industry to Mass-Produce Detectors for Next-Gen Cosmic Experiment, The commercial fabrication effort is intended to benefit this CMB-S4 experiment, ultraprecise magnetic field sensors known as SQUIDs (superconducting quantum interference devices), Ultrasensitive detectors key in sleuthing universe’s mysteries   

    From Lawrence Berkeley National Lab: “Scientists Team Up With Industry to Mass-Produce Detectors for Next-Gen Cosmic Experiment” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    January 17, 2019

    Berkeley Lab researcher leads effort to take specialized superconducting sensor-making processes into commercial production.

    1
    Crews work at the site of the POLARBEAR-2/Simons Array experiments in Chile. There are plans to combine data at this site with data collected near the South Pole for a next-generation cosmic microwave background experiment known as CMB-S4. (Credit: POLARBEAR Collaboration)

    Chasing clues about the infant universe in relic light known as the cosmic microwave background, or CMB, scientists are devising more elaborate and ultrasensitive detector arrays to measure the properties of this light with increasing precision.

    CMB per ESA/Planck

    To meet the high demand for these detectors that will drive next-generation CMB experiments, and for similar detectors to serve other scientific needs, researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) are pushing to commercialize the manufacturing process so that these detectors can be mass-produced quickly and affordably.

    Ultrasensitive detectors key in sleuthing universe’s mysteries

    The type of detector they are working to commercialize incorporates sensors that, when chilled to far-below-freezing temperatures, operate at the very edge of superconductivity – a state in which there is zero electrical resistance. Incorporated in the detector design is transition-edge sensor (TES) technology that can be tailored for ultrahigh sensitivity to temperature changes, among other measurements.

    The team is also working to commercialize the production of ultraprecise magnetic field sensors known as SQUIDs (superconducting quantum interference devices).

    2
    Superconducting SQUID

    In the current TES detector design, each detector array is fabricated on a silicon wafer and contains about 1,000 detectors. Hundreds of thousands of these detectors will be needed for a massive next-generation CMB experiment, dubbed CMB-S4.

    The SQUID amplifiers are designed to enable low-noise readout of signals from the detectors. They are intended to be seated near the detectors to simplify the assembly process and the operation of the next-generation detector arrays.

    More exacting measurements of the CMB light’s properties, including specifics on its polarization – directionality in the light – can help scientists peer more deeply into the universe’s origins, which in turn can lead to more accurate models and a richer understanding of the modern universe.

    Berkeley Lab researchers have a long history of pioneering achievements in the in-house design and development of new detectors for particle physics, nuclear physics, and astrophysics experiments. And while the detectors can be built in-house, scientists also considered the fact that commercial firms have access to state-of-the-art, high-throughput microfabricating machines and expertise in larger-scale manufacturing processes.

    So Aritoki Suzuki, a staff scientist in Berkeley Lab’s Physics Division, for the past several years has been working to transfer highly specialized detector fabrication techniques needed for new physics experiments to industry. The goal is to determine if it’s possible to produce a high volume of detector wafers more quickly, and at lower cost, than is possible at research labs.

    “What we are building here is a general technique to make superconducting devices at a company to benefit areas like astrophysics, the search for dark matter, quantum computing, quantum information science, and superconducting circuits in general,” said Suzuki, who has been working on advanced detector R&D for about a decade.

    This breed of sensors has also been enlisted in the hunt for a theorized nuclear process called neutrinoless double-beta decay that could help solve a riddle about the abundance of matter over antimatter in the universe, and whether the ghostly neutrino particle is its own antiparticle.

    Progress in transferring detector technology

    Progress toward commercial production of the specialized detectors has been promising. “We have demonstrated that detector performance from commercially fabricated detectors meet the requirements of typical CMB experiments,” Suzuki said.

    Work is underway to build the prototype detectors for a planned CMB experiment in Chile known as the Simons Observatory that may incorporate the commercially produced detectors.

    About 3 miles above sea level, in the Atacama Desert of Northern Chile, researchers have worked on successive generations of TES-based detector arrays for CMB-related experiments including POLARBEAR, POLARBEAR-2, the Simons Array, and the Simons Observatory.

    A detector array for two telescopes that are part of the POLARBEAR-2 and Simons Array experiments is now being fabricated at UC Berkeley’s Marvell Nanofabrication Laboratory by Berkeley Lab and UC Berkeley researchers. The effort will ultimately produce 7,600 detectors apiece for three telescopes. The first telescope in the Simons Array has just begun its commissioning run.

    The Simons Observatory project, which is now in a design and prototyping phase, will require about 80,000 detectors, half of which will be fabricated at the Marvell Nanofabrication Laboratory.

    3
    A POLARBEAR-2/Simons Array detector array. Multiple detector modules (right) will be tiled together to form a focal plane (left) containing 7,600 detectors. At the base of the detector modules are electronics components for detector data readout. (Credit: POLARBEAR Collaboration)

    These experiments are driving toward a CMB-S4 experiment that will combine detector arrays in Chile and near the South Pole to better resolve the cosmic microwave background and possibly help determine whether the universe underwent a brief period of incredible expansion known as inflation in its formative moments.

    The commercial fabrication effort is intended to benefit this CMB-S4 experiment, which will require a total of about 500,000 detectors. The current design calls for about 400 detector wafers that will each feature more than 1,000 detectors arranged on hexagonal silicon wafers measuring about six inches across. The wafers are designed to be tiled together in telescope arrays.

    Suzuki, who is part of a scientific board working on CMB-S4 along with other Berkeley Lab scientists, is collaboring with Adrian Lee, another board member who is also a physicist at Berkeley Lab and a UC Berkeley physics professor. It was Lee who pioneered microfabrication techniques at UC Berkeley to help speed the production of TES-containing detectors.

    In addition to the detector production at UC Berkeley’s nanofabrication laboratory, researchers have also built specialized superconducting readout electronics in a nearly dustless clean room space within the Microsystems Laboratory at Berkeley Lab.

    Before the introduction of higher-throughput manufacturing processes, detectors “were made one by one, by hand,” Suzuki noted.

    Suzuki labored to develop the latest 6-inch wafer design, which offers a production throughput advantage over the previously used 4-inch wafer designs. Older wafers had only about 100 detectors, which would have required the production of many more wafers to fully outfit a CMB-S4 experiment.

    The current detector design incorporates niobium, a superconducting metal, and other uncommon metals like palladium and manganese-doped aluminum alloy.

    “These are very unique metals that normally companies don’t touch. We use them to achieve the unique properties that we desire for these detectors,” Suzuki said.

    The effort has benefited from a Laboratory Directed Research and Development grant that Lee received in 2015 to explore commercial fabrication of the detectors. Also, the research team has received support from the federally supported Small Business Innovation Research program, and Suzuki has also received support from the DOE Early Career Research Program.

    3

    Suzuki has worked with Hypres Inc. of New York and STAR Cryoelectronics of Santa Fe, New Mexico, on the fabrication processes for the detectors, and worked with the University of New Mexico and STAR Cryoelectronics on the SQUID amplifiers. Suzuki said that working with the companies has been a productive process. “They gave us a lot of ideas,” he said, to help improve and streamline the processes.

    The industry-produced SQUID amplifiers will be used in one of the telescopes of the POLARBEAR-2/Simons Array experiment, Suzuki noted, and the design of these amplifiers could drive improvements in the readout electronics of a CMB-S4 experiment.

    As a next step in the effort to commercially fabricate detectors, a test run is planned this year to demonstrate fabrication quality and throughput.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 3:38 pm on January 3, 2019 Permalink | Reply
    Tags: , , , Electron spin, LBNL, SARPES detector, ,   

    From Lawrence Berkeley National Lab: “Revealing Hidden Spin: Unlocking New Paths Toward High-Temperature Superconductors” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    January 3, 2019

    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    Berkeley Lab researchers uncover insights into superconductivity, leading potentially to more efficient power transmission.

    1
    A research team led by Berkeley Lab’s Alessandra Lanzara (second from left) used a SARPES (spin- and angle-resolved photoemission spectroscopy) detector to uncover a distinct pattern of electron spins within the material. Co-lead authors are Kenneth Gotlieb (second from right) and Chiu-Yun Lin (right). The study’s co-authors include Chris Jozwiak of Berkeley Lab’s Advanced Light Source (left). (Credit: Peter DaSilva/Berkeley Lab)

    In the 1980s, the discovery of high-temperature superconductors known as cuprates upended a widely held theory that superconductor materials carry electrical current without resistance only at very low temperatures of around 30 Kelvin (or minus 406 degrees Fahrenheit). For decades since, researchers have been mystified by the ability of some cuprates to superconduct at temperatures of more than 100 Kelvin (minus 280 degrees Fahrenheit).

    Now, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have unveiled a clue into the cuprates’ unusual properties – and the answer lies within an unexpected source: the electron spin. Their paper describing the research behind this discovery was published on Dec. 13 in the journal Science.

    Adding electron spin to the equation

    Every electron is like a tiny magnet that points in a certain direction. And electrons within most superconductor materials seem to follow their own inner compass. Rather than pointing in the same direction, their electron spins haphazardly point every which way – some up, some down, others left or right.

    2
    With the spin resolution enabled by SARPES, Berkeley Lab researchers revealed magnetic properties of Bi-2212 that have gone unnoticed in previous studies. (Credit: Kenneth Gotlieb, Chiu-Yun Lin, et al./Berkeley Lab)

    When scientists are developing new kinds of materials, they usually look at the materials’ electron spin, or the direction in which the electrons are pointing. But when it comes to making superconductors, condensed matter physicists haven’t traditionally focused on spin, because the conventionally held view was that all of the properties that make these materials unique were shaped only by the way in which two electrons interact with each other through what’s known as “electron correlation.”

    But when a research team led by Alessandra Lanzara, a faculty scientist in Berkeley Lab’s Materials Sciences Division and a Charles Kittel Professor of Physics at UC Berkeley, used a unique detector to measure samples of an exotic cuprate superconductor, Bi-2212 (bismuth strontium calcium copper oxide), with a powerful technique called SARPES (spin- and angle-resolved photoemission spectroscopy), they uncovered something that defied everything they had ever known about superconductors: a distinct pattern of electron spins within the material.

    “In other words, we discovered that there was a well-defined direction in which each electron was pointing given its momentum, a property also known as spin-momentum locking,” said Lanzara. “Finding it in high-temperature superconductors was a big surprise.”

    A new map for high-temperature superconductors

    In the world of superconductors, “high temperature” means that the material can conduct electricity without resistance at temperatures higher than expected but still in extremely cold temperatures far below zero degrees Fahrenheit. That’s because superconductors need to be extraordinarily cold to carry electricity without any resistance. At those low temperatures, electrons are able to move in sync with each other and not get knocked by jiggling atoms, causing electrical resistance.

    And within this special class of high-temperature superconductor materials, cuprates are some of the best performers, leading some researchers to believe that they have potential use as a new material for building super-efficient electrical wires that can carry power without any loss of electron momentum, said co-lead author Kenneth Gotlieb, who was a Ph.D. student in Lanzara’s lab at the time of the discovery. Understanding what makes some exotic cuprate superconductors such as Bi-2212 work at temperatures as high as 133 Kelvin (about -220 degrees Fahrenheit) could make it easier to realize a practical device.

    Among the very exotic materials that condensed matter physicists study, there are two kinds of electron interactions that give rise to novel properties for new materials, including superconductors, said Gotlieb. Scientists who have been studying cuprate superconductors have focused on just one of those interactions: electron correlation.

    The other kind of electron interaction found in exotic materials is “spin-orbit coupling” – the way in which the electron’s magnetic moment interacts with atoms in the material.

    Spin-orbit coupling was often neglected in the studies of cuprate superconductors, because many assumed that this kind of electron interaction would be weak when compared to electron correlation, said co-lead author Chiu-Yun Lin, a researcher in the Lab’s Materials Sciences Division and a Ph.D. student in the Department of Physics at UC Berkeley. So when they found the unusual spin pattern, Lin said that although they were pleasantly surprised by this initial finding, they still weren’t sure whether it was a “true” intrinsic property of the Bi-2212 material, or an external effect caused by the way the laser light interacted with the material in the experiment.

    Shining a light on electron spin with SARPES

    Over the course of nearly three years, Gotlieb and Lin used the SARPES detector to thoroughly map out the spin pattern at Lanzara’s lab. When they needed higher photon energies to excite a wider range of electrons within a sample, the researchers moved the detector next door to Berkeley Lab’s synchrotron, the Advanced Light Source (ALS), a U.S. DOE Office of Science User Facility that specializes in lower energy, “soft” X-ray light for studying the properties of materials.

    LBNL/ALS

    The SARPES detector was developed by Lanzara, along with co-authors Zahid Hussain, the former ALS Division Deputy, and Chris Jozwiak, an ALS staff scientist. The detector allowed the scientists to probe key electronic properties of the electrons such as valence band structure.

    After tens of experiments at the ALS, where the team of researchers connected the SARPES detector to Beamline 10.0.1 so they could access this powerful light to explore the spin of the electrons moving with much higher momentum through the superconductor than those they could access in the lab, they found that Bi-2212’s distinct spin pattern – called “nonzero spin – was a true result, inspiring them to ask even more questions. “There remains many unsolved questions in the field of high-temperature superconductivity,” said Lin. “Our work provides new knowledge to better understand the cuprate superconductors, which can be a building block to resolve these questions.”

    Lanzara added that their discovery couldn’t have happened without the collaborative “team science” of Berkeley Lab, a DOE national lab with historic ties to nearby UC Berkeley. “This work is a typical example of where science can go when people with expertise across the scientific disciplines come together, and how new instrumentation can push the boundaries of science,” she said.

    Co-authors with Gotlieb, Lin, and Lanzara are Maksym Serbyn of the Institute of Science and Technology Austria, Wentao Zhang of Shanghai Jiao Tong University, Christopher L. Smallwood of San Jose State University, Christopher Jozwiak of Berkeley Lab, Hiroshi Eisaki of the National Institute of Advanced Industrial Science and Technology of Japan, Zahid Hussain of Berkeley Lab, and Ashvin Vishwanath, formerly of UC Berkeley and now with Harvard University and a Faculty Scientist in Berkeley Lab’s Materials Sciences Division.

    The work was supported by the DOE Office of Science.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:45 pm on December 17, 2018 Permalink | Reply
    Tags: , , LBNL, Lux Zeplin project, PMT's-photomultiplier tubes, ,   

    From Brown University: “Massive new dark matter detector gets its ‘eyes’” 

    Brown University
    From Brown University

    1
    The detector’s “eyes”
    Powerful light sensors assembled at Brown into two large arrays will keep watch on the LUX-ZEPLIN dark matter detector, looking for the tell-tale flashes of light that indicate interaction of a dark matter particle inside the detector. Credit: Nick Dentamaro

    LBNL Lux Zeplin project at SURF

    December 17, 2018
    Kevin Stacey

    Brown University researchers have assembled two massive arrays of photomultiplier tubes, powerful light sensors that will serve as the “eyes” for the LUX-ZEPLIN dark matter detector, which will start its search for dark matter particles in 2020.

    The LUX-ZEPLIN (LZ) dark matter detector, which will soon start its search for the elusive particles thought to account for a majority of matter in the universe, had the first of its “eyes” delivered late last week.

    The first of two large arrays of photomultiplier tubes (PMTs) — powerful light sensors that can detect the faintest of flashes — arrived last Thursday at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, where LZ is scheduled to begin its dark matter search in 2020. The second array will arrive in January. When the detector is completed and switched on, the PMT arrays will keep careful watch on LZ’s 10-ton tank of liquid xenon, looking for the telltale twin flashes of light produced if a dark matter particle bumps into a xenon atom inside the tank.

    The two arrays, each about 5 feet in diameter and holding a total of 494 PMTs, were shipped to South Dakota via truck from Providence, Rhode Island, where a team of researchers and technicians from Brown University spent the past six months painstakingly assembling them.

    “The delivery of these arrays is the pinnacle of an enormous assembly effort that we’ve executed here in our cleanroom at the Brown Department of Physics,” said Rick Gaitskell, a professor of physics at Brown University who oversaw the construction of the arrays. “For the last two years, we’ve been making sure that every piece that’s going into the devices is working as expected. Only by doing that can we be confident that everything will perform the way we want when the detector is switched on.”

    The Brown team has worked with researchers and engineers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and from Imperial College London to design, procure, test, and assemble all of the components of the array. Testing of the PMTs, which are manufactured by the Hamamatsu Corporation in Japan, was performed at Brown and at Imperial College “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    “The PMTs have already qualified for significant air miles, even before they started their 2,000-mile journey by road from Rhode Island to South Dakota,” Gaitskell said.

    Catching a WIMP

    Nobody knows exactly what dark matter is. Scientists can see the effects of its gravity in the rotation of galaxies and in the way light bends as it travels across the universe, but no one has directly detected a dark matter particle. The leading theoretical candidate for a dark matter particle is the WIMP, or weakly interacting massive particle. WIMPs can’t be seen because they don’t absorb, emit or reflect light. And they interact with normal matter only on very rare occasions, which is why they’re so hard to detect even when millions of them may be traveling through the Earth and everything on it each second.

    The LZ experiment, a collaboration of more than 250 scientists worldwide, aims to capture one of those fleetingly rare WIMP interactions, and thereby characterize the particles thought to make up more than 80 percent of the matter in the universe. The detector will be the most sensitive ever built, 50 times more sensitive than the LUX detector, which wrapped up its dark matter search at SURF in 2016.

    3
    This rendering shows a cutaway view of the LZ xenon tank (center), with PMT arrays at the top and bottom of the tank. (Credit: Greg Stewart/SLAC National Accelerator Laboratory)

    The PMT arrays are a critical part of the experiment. Each PMT is a six-inch-long cylinder that is roughly the diameter of a soda can. To form arrays large enough to monitor the entire LZ xenon target, hundreds of PMTs are assembled together within a circular titanium matrix. The array that will sit on top of the xenon target has 253 PMTs, while the lower array has 241.

    PMTs are designed to amplify weak light signals. When individual photons (particles of light) enter a PMT, they strike a photocathode. If the photon has sufficient energy, it causes the photocathode to eject one or more electrons. Those electrons strike then an electrode, which ejects more electrons. By cascading through a series of electrodes the original signal is amplified by over a factor of a million to create a detectable signal.

    LZ’s PMT arrays will need every bit of that sensitivity to catch the flashes associated with a WIMP interaction.

    “We could be looking for events emitting as few as 20 photons in a huge tank containing 10 tons of xenon, which is something that the human visual system wouldn’t be able to do,” Gaitskell said. “But it’s something these arrays can do, and we’ll need them to do it in order to see the signal from rare particle events.”

    The photons are produced by what’s known as a nuclear recoil event, which produces two distinct flashes. The first comes at the moment a WIMP bumps into a xenon nucleus. The second, which comes a few hundred microseconds afterward, is produced by the ricochet of the xenon atom that was struck. It bounces into the atoms surrounding it, which knocks a few electrons free. The electrons are then drifted by an electric field to the top of the tank, where they reach a thin layer of xenon gas that converts them into light.

    In order for those tiny flashes to be distinguishable from unwanted background events, the detector needs to be protected from cosmic rays and other kinds of radiation, which also cause liquid xenon to light up. That’s why the experiment takes place underground at SURF, a former gold mine, where the detector will be shielded by about a mile of rock to limit interference.

    A clean start

    The need to limit interference is also the reason that the Brown University team was obsessed with cleanliness while they assembled the arrays. The team’s main enemy was plain old dust.

    “When you’re dealing with an instrument that’s as sensitive as LZ, suddenly things you wouldn’t normally care about become very serious,” said Casey Rhyne, a Brown graduate student who had a leading role in building the arrays. “One of the biggest challenges we had to confront was minimizing ambient dust levels during assembly.”

    Each dust particle carries a minuscule amount of radioactive uranium and thorium decay products. The radiation is vanishingly small and poses no threat to people, but too many of those specks inside the LZ detector could be enough to interfere with a WIMP signal.

    4
    Much of the assembly work was done while the arrays sat inside PALACE, an ultraclean enclosure designed to keep the arrays dust-free. Nick Detamaro

    In fact, the dust budget for the LZ experiment calls for no more than one gram of dust in the entire 10-ton instrument. Because of all their nooks and crannies, the PMT arrays could be significant dust contributors if pains were not taken to keep them clean throughout construction.

    The Brown team performed most of its work in a “class 1,000” cleanroom, which allows no more than 1,000 microscopic dust particles per cubic foot of space. And within that cleanroom was an even more pristine space that the team dubbed “PALACE (PMT Array Lifting And Commissioning Enclosure).” PALACE was essentially an ultraclean exoskeleton where much of the actual array assembly took place. PALACE was a “class 10” space — no more than 10 dust particles bigger than one hundredth the width of a human hair per cubic foot.

    But the radiation concerns didn’t stop at dust. Before assembly of the arrays began, the team prescreened every part of every PMT tube to assess radiation levels.

    “We had Hamamatsu send us all of the materials that they were going to use for the PMT construction, and we put them in an underground germanium detector,” said Samuel Chan, a graduate student and PMT system team leader. “This detector is very good at detecting the radiation that the construction materials are emitting. If the intrinsic radiation levels were low enough in these materials, then we told Hamamatsu to go ahead and use them in the manufacture of these PMTs.”

    7
    A PMT is carefully inserted into the array inside PALACE. Nick Dentamaro

    The team is hopeful that all the work contributed over the past six months will pay dividends when LZ starts its WIMP search.

    “Getting everything right now will have a huge impact less than two years from now when we switch on the completed detector and we’re taking data,” Gaitskell said. “We’ll be able to see directly from that data how good of a job we and other people have done.”

    Given the major increase in dark matter search sensitivity that the LUX-ZEPLIN detector can deliver compared to previous experiments, the team hopes that this detector will finally identify and characterize the vast sea of stuff that surrounds us all. So far, the dark stuff has remained maddeningly elusive.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
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