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  • richardmitnick 3:18 pm on December 7, 2018 Permalink | Reply
    Tags: BNL, Combo of experimental techniques plots points in previously unmapped region of a high-temperature superconductor's "phase diagram.", Scientists Enter Unexplored Territory in Superconductivity Search   

    From Brookhaven National Lab: “Scientists Enter Unexplored Territory in Superconductivity Search” 

    From Brookhaven National Lab

    December 6, 2018

    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350

    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174

    Combo of experimental techniques plots points in previously unmapped region of a high-temperature superconductor’s “phase diagram.”

    2
    Brookhaven physicist Tonica Valla in the OASIS laboratory at Brookhaven National Laboratory.

    Scientists mapping out the quantum characteristics of superconductors—materials that conduct electricity with no energy loss—have entered a new regime. Using newly connected tools named OASIS at the U.S. Department of Energy’s Brookhaven National Laboratory, they’ve uncovered previously inaccessible details of the “phase diagram” of one of the most commonly studied “high-temperature” superconductors. The newly mapped data includes signals of what happens when superconductivity vanishes.

    “In terms of superconductivity, this may sound bad, but if you study some phenomenon, it is always good to be able to approach it from its origin,” said Brookhaven physicist Tonica Valla, who led the study just published in the journal Nature Communications. “If you have a chance to see how superconductivity disappears, that in turn might give insight into what causes superconductivity in the first place.”

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    Brookhaven physicist Ilya Drozdov, lead author on a new paper mapping out a previously unexplored region of the phase diagram of a common superconductor.

    Unlocking the secrets of superconductivity holds great promise in addressing energy challenges. Materials able to carry current over long distances with no loss would revolutionize power transmission, eliminate the need for cooling computer-packed data centers, and lead to new forms of energy storage, for example. The hitch is that, at present, most known superconductors, even the “high-temperature” varieties, must themselves be kept super cold to perform their current-carrying magic. So, scientists have been trying to understand the key characteristics that cause superconductivity in these materials with the goal of discovering or creating new materials that can operate at temperatures more practical for these everyday applications.

    The Brookhaven team was studying a well-known high-temperature superconductor made of layers that include bismuth-oxide, strontium-oxide, calcium, and copper-oxide (abbreviated as BSCCO). Cleaving crystals of this material creates pristine bismuth-oxide surfaces. When they analyzed the electronic structure of the pristine cleaved surface, they saw telltale signs of superconductivity at a transition temperature (Tc) of 94 Kelvin (-179 degrees Celsius)—the highest temperature at which superconductivity sets in for this well-studied material.

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    This phase diagram for BSCCO plots the temperature (T, in degrees Kelvin, on the y axis) at which superconductivity sets in as more and more charge vacancies, or “holes,” are doped into the material (horizontal, x axis). On the underdoped side of the “dome” (left), as more holes are added, the transition temperate increases to a maximum of 94 K, but as more holes are added, the transition temperature drops off. The red dashed line represents previously assumed dependence of superconductivity “dome,” while the black line represents the correct dependence, obtained from the new data (black dots). This was the first time scientists were able to create highly overdoped samples, allowing them to explore the part of the phase diagram shaded in yellow where superconductivity disappears. Tracking the disappearance may help them understand what causes superconductivity to occur in the first place.

    The team then heated samples in ozone (O3) and found that they could achieve high doping levels and explore previously unexplored portions of this material’s phase diagram, which is a map-like graph showing how the material changes its properties at different temperatures under different conditions (similar to the way you can map out the temperature and pressure coordinates at which liquid water freezes when it is cooled, or changes to steam when heated). In this case, the variable the scientists were interested in was how many charge vacancies, or “holes,” were added, or “doped” into the material by the exposure to ozone. Holes facilitate the flow of current by giving the charges (electrons) somewhere to go.

    “For this material, if you start with the crystal of ‘parent’ compound, which is an insulator (meaning no conductivity), the introduction of holes results in superconductivity,” Valla said. As more holes are added, the superconductivity gets stronger and at higher temperatures up to a maximum at 94 Kelvin, he explained. “Then, with more holes, the material becomes ‘over-doped,’ and Tc goes down—for this material, to 50 K.

    “Until this study, nothing past that point was known because we couldn’t get crystals doped above that level. But our new data takes us to a point of doping way beyond the previous limit, to a point where Tc is not measurable.”

    Said Valla, “That means we can now explore the entire dome-shaped curve of superconductivity in this material, which is something that nobody has been able to do before.”

    5
    The Fermi surface, or the highest occupied state in the electronic structure, allows direct determination of the doping level. This picture shows the Fermi surface of the highly overdoped, non-superconducting BSCCO where the holes were added into the material by exposure to ozone.

    The team created samples heated in a vacuum (to produce underdoped material) and in ozone (to make overdoped samples) and plotted points along the entire superconducting dome. They discovered some interesting characteristics in the previously unexplored “far side” of the phase diagram.

    “What we saw is that things become much simpler,” Valla said. Some of the quirkier characteristics that exist on the well-explored side of the map and complicate scientists’ understanding of high-temperature superconductivity—things like a “pseudogap” in the electronic signature, and variations in particle spin and charge densities—disappear on the overdoped far side of the dome.

    “This side of the phase diagram is somewhat like what we expect to see in more conventional superconductivity,” Valla said, referring to the oldest known metal-based superconductors.

    “When superconductivity is free of these other things that complicate the picture, then what is left is superconductivity that perhaps is not that unconventional,” he added. “We still might not know its origin, but on this side of the phase diagram, it looks like something that theory can handle more easily, and it gives you a simpler way of looking at the problem to try to understand what is going on.”

    The team created samples heated in a vacuum (to produce underdoped material) and in ozone (to make overdoped samples) and plotted points along the entire superconducting dome. They discovered some interesting characteristics in the previously unexplored “far side” of the phase diagram.

    “This side of the phase diagram is somewhat like what we expect to see in more conventional superconductivity,” Valla said, referring to the oldest known metal-based superconductors.

    “When superconductivity is free of these other things that complicate the picture, then what is left is superconductivity that perhaps is not that unconventional,” he added. “We still might not know its origin, but on this side of the phase diagram, it looks like something that theory can handle more easily, and it gives you a simpler way of looking at the problem to try to understand what is going on.”

    ____________________________________________________________

    Combination of Uniquely Connected Tools

    The tools scientists used in this study are part of a suite of three that Brookhaven Lab has built named OASIS to explore materials such as high-temperature superconductors. The idea is to connect the tools with ultra-high vacuum sample-transfer lines so scientists can create and study samples using multiple techniques without ever exposing the experimental materials to the atmosphere (and all its potentially “contaminating” substances, including oxygen). OASIS is a tool that connects sample preparation capabilities of oxide molecular beam epitaxy (OMBE) synthesis with electronic structure characterization tools: angle resolved photoemission spectroscopy (ARPES) and spectroscopic imaging-scanning tunneling microscopy (SI-STM).

    In this case, the scientists used ARPES to examine the samples’ electronic structure. ARPES uses light to measure “electronic excitations” in the sample. These measurements provide a sort of electronic fingerprint that describes the energy and movement of electrons and how they interact with other types of excitations—say, distortions or vibrations in the crystal lattice, variations in temperature, or imperfections or impurities.

    After studying pristine samples, the scientists transported them via vacuum tube to an OMBE machine where they could anneal (heat) the crystals under a steady stream of ozone.

    The connected tools allow the scientists to transfer samples back and forth to study the material both before and after heating in both a vacuum and ozone to create both the underdoped and overdoped samples needed to map out the phase diagram.

    In this paper, the spectroscopic imaging-scanning tunneling microscope (SI-STM) connected to the previously mentioned ARPES and OMBE modules was not employed. A complementary SI-STM study of the BSCCO samples is currently ongoing.

    ____________________________________________________________

    See the full article here .


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    Please help promote STEM in your local schools.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 10:13 am on November 19, 2018 Permalink | Reply
    Tags: , Aside from reducing the time it takes to complete an experiment a faster TXM can collect more valuable data from samples, BNL, FXI-Full Field X-ray Imaging beamline, See a sample in 3-D and in real time, TXM-Transmission x-ray microscopy   

    From Brookhaven National Lab: “Making X-ray Microscopy 10 Times Faster” 

    From Brookhaven National Lab

    November 19, 2018
    Stephanie Kossman
    skossman@bnl.gov

    1
    NSLS-II scientists Scott Coburn (left) and Wah-Keat Lee (right) are shown at the Full Field X-ray Imaging beamline, where scientists and engineers have built a transmission x-ray microscope that can image samples 10 times faster than previously possible.

    Microscopes make the invisible visible. And compared to conventional light microscopes, transmission x-ray microscopes (TXM) can see into samples with much higher resolution, revealing extraordinary details. Researchers across a wide range of scientific fields use TXM to see the structural and chemical makeup of their samples—everything from biological cells to energy storage materials.

    Now, scientists at the National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Brookhaven National Laboratory—have developed a TXM that can image samples 10 times faster than previously possible. Their research is published in Applied Physics Letters.

    “We have significantly improved the speed of x-ray microscopy experiments,” said Wah-Keat Lee, lead scientist at NSLS-II’s Full Field X-ray Imaging (FXI) beamline, where the microscope was built. At FXI, Lee and his colleagues reduced the time it takes a TXM to image samples in 3-D from over 10 minutes to just one minute, while still producing images with exceptional 3-D resolution—below 50 nanometers, or 50 billionths of a meter. “This breakthrough will enable scientists to visualize their samples much faster at FXI than at similar instruments around the world,” Lee said.

    Aside from reducing the time it takes to complete an experiment, a faster TXM can collect more valuable data from samples.

    2
    The research team at NSLS-II’s Full Field X-ray Imaging beamline. Pictured from left to right are Xianghui Xiao, Weihe Xu, Huijuan Xu, Mingyuan Ge, Wah-Keat Lee, Scott Coburn, Kazimierz Gofron, and Evgeny Nazaretski.

    “The holy grail of almost all imaging techniques is to be able to see a sample in 3-D and in real time,” Lee said. “The speed of these experiments is relevant because we want to observe changes that happen quickly. There are many structural and chemical changes that happen on different time scales, so a faster instrument can see a lot more. For example, we have the ability to track how corrosion happens in a material, or how well various parts of a battery are performing.”

    To offer these capabilities at FXI, the team needed to build a TXM using the latest developments in ultrafast nano-positioning (a method of moving a sample while limiting vibrations), sensing (a method of tracking sample movement), and control. The new microscope was developed in-house at Brookhaven Lab through a collaborative effort between the engineers, beamline staff, and research and development teams at NSLS-II.

    The researchers said developing superfast capabilities at FXI also strongly depended on the advanced design of NSLS-II.

    1
    4
    5
    6
    Above four animated images-Scientists used NSLS-II’s Full Field X-ray Imaging beamline to create a 3-D animation of silver dendrite growth on copper during a chemical reaction.

    “Our ability to make FXI more than 10 times faster than any other instrument in the world is also due to the powerful x-ray source at NSLS-II,” Lee said. “At NSLS-II, we have devices called damping wigglers, which are used to achieve the very small electron beams for the facility. Fortunately for us, these devices also produce a very large number of x-rays. The amount of these powerful x-rays directly relates to the speed of our experiments.”

    Using the new capabilities at FXI, the researchers imaged the growth of silver dendrites on a sliver of copper. In a single minute, the beamline captured 1060 2-D images of the sample and reconstructed them to form a 3-D snapshot of the reaction. Repeating this, the researchers were able to form a minute-by-minute, 3-D animation of the chemical reaction.

    “We chose to image this reaction because it demonstrates the power of FXI,” said Mingyuan Ge, lead author of the research and a scientist at NSLS-II. “The reaction is well-known, but it has never been visualized in 3-D with such a fast acquisition time. In addition, our spatial resolution is 30 to 50 times finer than optical microscopy used in the past.”

    With the completion of this research, FXI has begun its general user operations, welcoming researchers from around the world to use the beamline’s advanced capabilities.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 4:16 pm on November 9, 2018 Permalink | Reply
    Tags: , BNL, NSLS-II’s Coherent Soft X-ray scattering (CSX) beamline, The metal-insulator transition in the correlated material magnetite is a two-step process, Unlocking the Secrets of Metal-Insulator Transitions, , XPCS- x-ray photon correlation spectroscopy   

    From Brookhaven National Lab: “Unlocking the Secrets of Metal-Insulator Transitions” 

    From Brookhaven National Lab

    November 8, 2018

    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174 |

    Written by Allison Gasparini

    X-ray photon correlation spectroscopy at NSLS-II’s CSX beamline used to understand electrical conductivity transitions in magnetite.

    1
    Professor Roopali Kukreja from the University of California in Davis and the CSX team Wen Hu, Claudio Mazzoli, and Andi Barbour prepare the beamline for the next set of experiments.

    By using an x-ray technique available at the National Synchrotron Light Source II (NSLS-II), scientists found that the metal-insulator transition in the correlated material magnetite is a two-step process. The researchers from the University of California Davis published their paper in the journal Physical Review Letters. NSLS-II, a U.S. Department of Energy (DOE) Office of Science user facility located at Brookhaven National Laboratory, has unique features that allow the technique to be applied with stability and control over long periods of time.

    “Correlated materials have interesting electronic, magnetic, and structural properties, and we try to understand how those properties change when their temperature is changed or under the application of light pulses, or an electric field” said Roopali Kukreja, a UC Davis professor and the lead author of the paper. One such property is electrical conductivity, which determines whether a material is metallic or an insulator.

    If a material is a good conductor of electricity, it is usually metallic, and if it is not, it is then known as an insulator. In the case of magnetite, temperature can change whether the material is a conductor or insulator. For the published study, the researchers’ goal was to see how the magnetite changed from insulator to metallic at the atomic level as it got hotter.

    In any material, there is a specific arrangement of electrons within each of its billions of atoms. This ordering of electrons is important because it dictates a material’s properties, for example its conductivity. To understand the metal-insulator transition of magnetite, the researchers needed a way to watch how the arrangement of the electrons in the material changed with the alteration of temperature.

    “This electronic arrangement is related to why we believe magnetite becomes an insulator,” said Kukreja. However, studying this arrangement and how it changes under different conditions required the scientists to be able to look at the magnetite at a super-tiny scale.

    2
    Roopali Kukreja (L), the lead author of the paper with Andi Barbour (R), CSX beamline scientist, work closely together while setting up the next set of measurements.

    The technique, known as x-ray photon correlation spectroscopy (XPCS), available at NSLS-II’s Coherent Soft X-ray scattering (CSX) beamline, allowed the researchers to look at how the material changed at the nanoscale—on the order of billionths of a meter.

    “CSX is designed for soft x-ray coherent scattering. This means that the beamline exploits our ultrabright, stable and coherent source of x-rays to analyze how the electron’s arrangement changes over time,” explained Andi Barbour, a CSX scientist who is a coauthor on the paper. “The excellent stability allows researchers to investigate tiny variations over hours so that the intrinsic electron behavior in materials can be revealed.”

    However, this is not directly visible so XPCS uses a trick to reveal the information.

    “The XPCS technique is a coherent scattering method capable of probing dynamics in a condensed matter system. A speckle pattern is generated when a coherent x-ray beam is scattered from a sample, as a fingerprint of its inhomogeneity in real space,” said Wen Hu, a scientist at CSX and co-author of the paper.

    Scientists can then apply different conditions to their material and if the speckle pattern changes, it means the electron ordering in the sample is changing. “Essentially, XPCS measures how much time it takes for a speckle’s intensity to become very different from the average intensity, which is known as decorrelation,” said Claudio Mazzoli, the lead beamline scientist at the CSX beamline. “Considering many speckles at once, the ensemble decorrelation time is the signature of the dynamic timescale for a given sample condition.”

    The technique revealed that the metal-insulator transition is not a one step process, as was previously thought, but actually happens in two steps.

    “What we expected was that things would go faster and faster while warming up. What we saw was that things get faster and faster and then they slow down. So the fast phase is one step and the second step is the slowing down, and that needs to happen before the material becomes metallic,” said Kukreja. The scientists suspect that the slowing down occurs because, during the phase change, the metallic and insulating properties actually exist at the same time in the material.

    “This study shows that these nanometer length scales are really important for these materials,” said Kukreja. “We can’t access this information and these experimental parameters anywhere else than at the CSX beamline of NSLS-II.”

    This research was funded by the National Science Foundation, the Air Force Office of Scientific Research, and the University of California’s Multicampus Research Programs and Initiatives.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

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    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 3:55 pm on November 9, 2018 Permalink | Reply
    Tags: BNL, Minerva NVIDIA's latest deep learning high-performance computing system, the DGX-2   

    From Brookhaven National Lab: “Leading-edge AI Computing System now at Home with Brookhaven Lab’s Computational Science Initiative” 

    From Brookhaven National Lab

    Minerva, NVIDIA’s latest deep learning high-performance computing system, the DGX-2, now is part of Brookhaven’s Computational Science Initiative. Photo courtesy of NVIDIA

    November 6, 2018
    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174 |

    Written by Charity Plata

    The Computational Science Initiative (CSI) at the U.S. Department of Energy’s Brookhaven National Laboratory now hosts one of the newest computing systems aimed at enhancing the speed and scale for conducting diverse scientific research: the NVIDIA® DGX-2™ Artificial Intelligence supercomputer.

    Designed to “take on the world’s most complex artificial intelligence challenges,” the NVIDIA DGX-2 at Brookhaven is one of the first available worldwide. At the Lab, the NVIDIA DGX-2, nicknamed “Minerva,” will serve as a user-accessible multipurpose machine focused on computer science research, machine learning, and data-intensive workloads.

    According to Adolfy Hoisie, who directs Brookhaven’s Computing for National Security Department, having the NVIDIA DGX-2’s compute power, which includes a 2-petaflops graphics processing unit (GPU) accelerator made possible by a scalable architecture built on the NVIDIA NVSwitch™ AI network fabric, will afford opportunities for diverse research pursuits with impact across the laboratory.

    In the area of systems architecture research, Hoisie expects that the NVIDIA DGX-2 will provide insights in evaluating the performance, power, and reliability of state-of-the-art computing technologies for various workloads.

    Because the NVIDIA DGX-2 specifically was designed to tackle the largest data sets and most computationally intensive and complex models, it also will play an important role in the Lab’s machine learning efforts. One such beneficiary will be the ExaLearn collaboration, an Exascale Computing Project co-design center featuring eight DOE national laboratories and led by CSI’s Deputy Director, Francis J. Alexander. The ExaLearn team primarily is developing machine learning software for exascale applications.

    The NVIDIA DGX-2 also will be engaged as part of CSI’s ongoing management, development, and discovery associated with the analysis and interpretation of high-volume, high-velocity heterogeneous scientific data.

    “We will expose the NVIDIA DGX-2 to data-intensive workloads for many programs, such as those of import to DOE science programs at the Lab’s Office of Science User Facilities—including the Relativistic Heavy Ion Collider, National Synchrotron Light Source II, and Center for Functional Nanomaterials—and to Department of Defense (DoD) data-intensive workloads of interest,” Hoisie explained. “Given significant bandwidth in and out of the system, we can pursue data analyses in multiple paradigms, for example, streaming data or fast access to vast amounts of data from Brookhaven Lab’s massive scientific databases. Such improvements will afford tremendous strides in data analyses within the Lab’s core high energy physics, nuclear physics, biological, atmospheric, and energy systems science areas and cryogenic technologies, as well as for specific research areas in computing sciences of interest to DOE and DoD.”

    CSI’s DGX-2 also will be a resource for NVIDIA as part of a collaboration. As research involving the system advances, its capability in impacting applications, speed to solutions, or even markers of its own overall performance will be shared between Brookhaven Lab and NVIDIA developers.

    DGX-2 is the newest addition to NVIDIA’s portfolio of AI supercomputers, which began with the DGX-1, introduced in 2016. The DGX-2 brings new innovations to AI, including the integration of 16 fully interconnected NVIDIA Tesla® Tensor Core V100 graphics processing units with 512 gigabytes of GPU memory.

    “We built the NVIDIA DGX-2 to solve the world’s most complex AI challenges, so we’re delighted that Brookhaven National Laboratory will put its innovations to use to further real-world science,” said Charlie Boyle, senior director of DGX Systems at NVIDIA. “The Lab’s researchers will be able to tap into the system’s 16 NVIDIA Tesla V100 Tensor Core GPUs—delivering two petaflops of computational performance—to help address opportunities of national importance.”

    For information about accessing the DGX-2 at Brookhaven Lab, please contact Adolfy Hoisie (ahoisie@bnl.gov).

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 9:37 pm on October 5, 2018 Permalink | Reply
    Tags: 'Choosy' Electronic Correlations Dominate Metallic State of Iron Superconductor, , BNL, , , HTS-high-temperature superconductors, , ,   

    From Brookhaven National Lab: “‘Choosy’ Electronic Correlations Dominate Metallic State of Iron Superconductor” 

    From Brookhaven National Lab

    October 3, 2018
    Ariana Tantillo
    atantillo@bnl.gov

    Finding could lead to a universal explanation of how two radically different types of materials—an insulator and a metal—can perfectly carry electrical current at relatively high temperatures.

    1
    Scientists discovered strong electronic correlations in certain orbitals, or energy shells, in the metallic state of the high-temperature superconductor iron selenide (FeSe). A schematic of the arrangement of the Se and Fe atoms is shown on the left; on the right is an image of the Se atoms in the termination layer of an FeSe crystal. Only the electron orbitals from the Fe atoms contribute to the orbital selectivity in the metallic state.

    Two families of high-temperature superconductors (HTS)—materials that can conduct electricity without energy loss at unusually high (but still quite cold) temperatures—may be more closely related than scientists originally thought.

    Beyond their layered crystal structures and the fact that they become superconducting when “doped” with atoms of other elements and cooled to a critical temperature, copper-based and iron-based HTS seemingly have little in common. After all, one material is normally an insulator (copper-based), and the other is a metal (iron-based). But a multi-institutional team of scientists has now presented new evidence suggesting that these radically different materials secretly share an important feature: strong electronic correlations. Such correlations occur when electrons move together in a highly coordinated way.

    “Theory has long predicted that strong electronic correlations can remain hidden in plain sight in a Hund’s metal,” said team member J.C. Seamus Davis, a physicist in the Condensed Matter Physics and Materials Science at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and the James Gilbert White Distinguished Professor in the Physical Sciences at Cornell University. “A Hund’s metal is a unique new type of electronic fluid in which the electrons from different orbitals, or energy shells, maintain very different degrees of correlation as they move through the material. By visualizing the orbital identity and correlation strength for different electrons in the metal iron selenide (FeSe), we discovered that orbital-selective strong correlations are present in this iron-based HTS.”

    It is yet to be determined if such correlations are characteristic of iron-based HTS in general. If proven to exist across both families of materials, they would provide the universal key ingredient in the recipe for high-temperature superconductivity. Finding this recipe has been a holy grail of condensed matter physics for decades, as it is key to developing more energy-efficient materials for medicine, electronics, transportation, and other applications.

    Experiment meets theory

    Since the discovery of iron-based HTS in 2008 (more than 20 years after that of copper-based HTS), scientists have been trying to understand the behavior of these unique materials. Confusion arose immediately because high-temperature superconductivity in copper-based materials emerges from a strongly correlated insulating state, but in iron-based HTS, it always emerges from a metallic state that lacks direct signatures of correlations. This distinction suggested that strong correlations were not essential—or perhaps even relevant—to high-temperature superconductivity. However, advanced theory soon provided another explanation. Because Fe-based materials have multiple active Fe orbitals, intense electronic correlations could exist but remain hidden due to orbital selectivity in the Hund’s metal state, yet still generate high-temperature superconductivity.

    In this study, recently described in Nature Materials, the team—including Brian Andersen of Copenhagen University, Peter Hirschfeld of the University of Florida, and Paul Canfield of DOE’s Ames National Laboratory—used a scanning tunneling microscope to image the quasiparticle interference of electrons in FeSe samples synthesized and characterized at Ames National Lab. Quasiparticle interference refers to the wave patterns that result when electrons are scattered due to atomic-scale defects—such as impurity atoms or vacancies—in the crystal lattice.

    2
    The spectroscopic imaging scanning tunneling microscope used for this study, in three different views.

    Spectroscopic imaging scanning tunneling microcopy can be used to visualize these interference patterns, which are characteristic of the microscopic behavior of electrons. In this technique, a single-atom probe moves back and forth very close to the sample’s surface in extremely tiny steps (as small as two trillionths of a meter) while measuring the amount of electrical current that is flowing between the single atom on the probe tip and the material, under an applied voltage.

    Their analysis of the interference patterns in FeSe revealed that the electronic correlations are orbitally selective—they depend on which orbital each electron comes from. By measuring the strength of the electronic correlations (i.e., amplitude of the quasiparticle interference patterns), they determined that some orbitals show very weak correlation, whereas others show very strong correlation.

    The next question to investigate is whether the orbital-selective electronic correlations are related to superconductivity. If the correlations act as a “glue” that binds electrons together into the pairs required to carry superconducting current—as is thought to happen in the copper-oxide HTS—a single picture of high-temperature superconductivity may emerge.

    Experimental studies were carried out by the former Center for Emergent Superconductivity, a DOE Energy Frontier Research Center at Brookhaven, and the research was supported by DOE’s Office of Science, the Moore Foundation’s Emergent Phenomena in Quantum Physics (EPiQS) Initiative, and a Lundbeckfond Fellowship.

    See the full article here .


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    Please help promote STEM in your local schools.

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    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 11:00 am on September 28, 2018 Permalink | Reply
    Tags: , BNL, , GRIK1, How a Molecular Signal Helps Plant Cells Decide When to Make Oil, How a sugar-signaling molecule helps regulate oil production in plant cells, KIN10, Microscale thermophoresis, The work could point to new ways to engineer plants to produce substantial amounts of oil for use as biofuels or in the production of other oil-based products, Trehalose 6-phosphate (T6P)   

    From Brookhaven National Lab: “How a Molecular Signal Helps Plant Cells Decide When to Make Oil” 

    From Brookhaven National Lab

    September 24, 2018
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350

    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174

    Details of mechanism suggest new strategy for engineering plants to make more oil.

    1
    Jantana Keereetaweep, John Shanklin, and Zhiyang Zhai prepare samples for studying the biochemical pathways that regulate oil production in plants.

    A study at the U.S. Department of Energy’s Brookhaven National Laboratory identifies new details of how a sugar-signaling molecule helps regulate oil production in plant cells. As described in a paper appearing in the journal The Plant Cell, the work could point to new ways to engineer plants to produce substantial amounts of oil for use as biofuels or in the production of other oil-based products.

    The study builds on previous research led by Brookhaven Lab biochemist John Shanklin that established clear links between a protein complex that senses sugar levels in plant cells (specifically a subunit called KIN10) and another protein that serves as the “on switch” for oil production (WRINKLED1) [The Plant Cell]. Using this knowledge, Shanklin’s team recently demonstrated that they could use combinations of genetic variants that increase sugar accumulation in plant leaves to drive up oil production. The new work provides a more detailed understanding of the link between sugar signaling and oil production, identifying precisely which molecules regulate the balance and how.

    “If you were a cell, you’d want to know if you should be making new compounds or breaking existing ones down,” said Shanklin. “Making oil is demanding; you want to make it when you have lots of energy—which in cells is measured by the amount of sugar available. By understanding how the availability of sugar drives oil production, we hope to find ways to get plants to boost the priority of making oil.”

    The team’s earlier research revealed some key biochemical details of the sugar-oil balancing act. Specifically, they found that when sugar levels are low, the KIN10 portion of the sugar-sensing complex shuts off oil production by triggering degradation of the oil “on” switch (WRINKLED1). High sugar levels somehow prevented this degradation, leaving the on-switch protein stabilized to crank out oil. But the scientists didn’t understand exactly how.

    For the new paper, first authors Zhiyang Zhai and Jantana Keereetaweep led a detailed investigation to unravel how these molecular players interact to drive up oil production when sugar is abundant.

    The team used an emerging technique, called microscale thermophoresis, which uses fluorescent dyes and heat to precisely measure the strength of molecular interactions.

    “You label the molecules with a fluorescent dye and measure how they move away from a heat source,” Shanklin explained. “Then, if you add another molecule that binds to the labeled molecule, it changes the rate at which the labeled molecule moves away from the heat.”

    “Jan and Zhiyang’s rapid application of this novel technique to this tough research problem was key to solving it,” Shanklin said.

    3
    When a plant is low on sugar (left), a cascade of molecular interactions degrades (DEG) a protein (W) that turns on fatty acid synthesis (FAS). However, when sugar levels are high (right), key steps in this process are blocked, leaving the W protein intact to start fatty acid (oil) production. KEY: K = KIN10, G = GRIK1, P = phosphoryl group, W = WRINKLED1, FAS = fatty acid synthesis, DEG = degradation, T6P = trehalose 6-phosphate. Faded molecules and pathways are less active than those shown in bold colors.

    Among the substances included in the study was a molecule known as trehalose 6-phosphate (T6P), the levels of which rise and fall with those of sugar. The study revealed that T6P interacts directly with the KIN10 component of the sugar-sensing complex. And it showed how that binding interferes with KIN10’s ability to shut off oil biosynthesis.

    “By measuring the interactions among many different molecules, we determined that the sugar-signaling molecule, T6P, binds with KIN10 and interferes with its interaction with a previously unidentified intermediate in this process, known as GRIK1, which is needed for KIN10 to tag WRINKLED1 for destruction. This explains how the signal affects the chain of events and leads to increased oil production,” Shanklin said. “It’s not just sugar but the signaling molecule that rises and falls with sugar that inhibits the oil shut-off mechanism.”

    To put this knowledge into action to increase oil production, the scientists will need even more details. So, the next step will be to get a close-up look at the interaction of T6P with its target protein, KIN10, at Brookhaven’s National Synchrotron Light Source II (NSLS-II). This DOE Office of Science user facility produces extremely bright x-rays, which the team will use to reveal exactly how the interacting molecules fit together.

    “With NSLS-II at Brookhaven Lab, we are in the perfect place to bring this research to the next stage,” Shanklin said. “There are unique tools available at the Light Source that will allow us to add atomic-level details to the interactions that we discovered.”

    BNL NSLS-II

    And those details could point to ways to change the sequence of KIN10, T6P’s target protein, to mimic the effects of the interaction and modify the cell’s regulatory circuitry to prioritize the production of oil.

    This work was funded by the DOE Office of Science. John Lunn and Regina Feil from the Max Planck Institute of Molecular Plant Physiology in Potsdam-Golm, Germany, collaborated on this study.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 9:07 am on September 2, 2018 Permalink | Reply
    Tags: , , BNL, David Livoti,   

    From Brookhaven National Lab: “Meet David Livoti: Radiofrequency Technician in Collider-Accelerator Department” 

    From Brookhaven National Lab

    August 31, 2018
    Rebecca Wilkin
    rebeccalwilkin@gmail.com

    Former intern now employee helps to maintain radiofrequency systems for particle accelerators.

    1
    Former intern David Livoti is now a full-time employee in the radiofrequency (RF) group of the C-AD complex, where he’s part of a team of technicians that maintains RF systems for the Lab’s particle accelerators. No image credit.

    Growing up, David Livoti spent his summers working at libraries and garden centers near his home in Center Moriches. Then, in 2017, he landed his first internship just a few minutes down the road at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, as a participant in the Office of Science’s Science Undergraduate Laboratory Internships (SULI) program. He quickly developed a passion for designing and studying the performance of electronics while building devices to measure snowfall amounts in Brookhaven’s Department of Environmental Science. One year later, Livoti is now helping to maintain acceleration systems for the Lab’s particle accelerators as a radiofrequency technician.

    “I like the atmosphere here at Brookhaven,” said Livoti, who graduated from Farmingdale State College last December with a dual degree in electrical and computer engineering. “I wanted to be in the research and design field, and I figured what better place to start a career than at a national laboratory where the most advanced research and design is done.”

    While interning under the direction of engineer Scott Smith, Livoti and fellow interns developed a machine that monitors snowfall accumulation—an improvement over the standard method of monitoring snowfall. That tedious task required taking manual measurements with a ruler every six hours!

    “The conventional method of measuring snow is archaic,” said Livoti, who completed all of the electronics and programming for the new device.

    The new device, developed in collaboration with the National Weather Service, has an electronic sensor that operates using sound waves, similar to the way sonar devices measure ocean depths. As snow accumulates, the sensor sends out sound waves to measure the change in distance between itself and the high point of accumulated snow piled up on a retractable table below. When the snow builds up to a certain point, the pre-programmed table tilts downward and the snow slides off, allowing the sensor to start measuring again, adding the additional accumulation to the running total.

    “This new, solar-powered device could help scientists determine snowfall rates more accurately, and it eliminates the task of taking manual measurements,” said Smith, who recently submitted the design for a patent. He noted that Livoti played a prominent role in building the device.

    “David has an incredible work ethic—he came to the lab early, stayed here late, and was relentless when it came to figuring out why something wasn’t working,” Smith said. “He’s also easy to get along with, and he has a great personality.”

    Hoping to continue his work with programming and electronics, Livoti applied for a position at the Lab after finishing his last semester of college. Within one month, he was hired as a technician in the radiofrequency (RF) group of the Collider-Accelerator Department (C-AD).

    The 23-year-old now works in the radiofrequency (RF) group of the C-AD complex, where he’s part of a team of technicians that maintains the RF systems. RF systems generate electric fields that control particles circulating in particle accelerators, including the Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science user facility for nuclear physics research that collides protons and/or heavy ions so scientists can study the building blocks of matter.

    “I enjoy maintaining the accelerators when they’re running, because it’s cool to see what the physicists are studying,” Livoti said. “But I also like when the accelerators are shut down, because that’s when the technicians get to experiment.”

    As part of the RF group, Livoti is assisting the lead engineers in maintaining and troubleshooting high power RF amplifiers and cavities that are integral parts of the C-AD complex. In addition, he is learning new technologies and conducting tests on solid-state and vacuum-tube amplifiers, as well as learning to program and use devices that control power supplies and monitor the status of other accelerator subcomponents.

    Livoti plans to continue this research and someday obtain a master’s degree in electrical engineering. When he isn’t busy maintaining and testing RF systems, he spends his time snowboarding and playing softball in the Lab’s league.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 8:09 pm on August 23, 2018 Permalink | Reply
    Tags: 3-D x-ray imaging that can visualize bulky materials in great detail, , BNL, called Multilayer Laue lenses (MLLs), HXN’s special optics, Novel X-Ray Optics Boost Imaging Capabilities at NSLS-II, ,   

    From Brookhaven National Lab: “Novel X-Ray Optics Boost Imaging Capabilities at NSLS-II” 

    From Brookhaven National Lab

    August 23, 2018
    Rebecca Wilkin
    rebeccalwilkin@gmail.com

    Brookhaven Lab scientists capture high-resolution, 3-D images of thick materials more efficiently than ever before.

    1
    NSLS-II scientist Hande Öztürk stands next to the Hard X-ray Nanoprobe (HXN) beamline, where her research team developed the new x-ray imaging technique. No photo credit.

    Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new approach to 3-D x-ray imaging that can visualize bulky materials in great detail—an impossible task with conventional imaging methods. The novel technique could help scientists unlock clues about the structural information of countless materials, from batteries to biological systems.

    The scientists developed their approach at Brookhaven’s National Synchrotron Light Source II (NSLS-II)—a DOE Office of Science User Facility where scientists use ultra-bright x-rays to reveal details at the nanoscale. The team is located at NSLS-II’s Hard X-ray Nanoprobe (HXN) beamline, an experimental station that uses advanced lenses to offer world-leading resolution, all the way down to 10 nanometers—about one ten-thousandth the diameter of a human hair.

    HXN produces remarkably high-resolution images that can provide scientists with a comprehensive view of different material properties in 2-D and 3-D. The beamline also has a unique combination of in situ and operando capabilities—methods of studying materials in real-life operating conditions. However, scientists who use x-ray microscopes have been restricted by the size and thickness of the materials they can study.

    “The x-ray imaging community is still facing major challenges in fully exploiting the potential of beamlines like HXN, especially for obtaining high-resolution details from thick samples,” said Yong Chu, lead beamline scientist at HXN. “Obtaining quality, high-resolution images can become challenging when a material is thick—that is, thicker than the x-ray optics’ depth of focus.”

    Now, scientists at HXN have developed an efficient approach to studying thick samples without sacrificing the excellent resolution that HXN provides. They describe their approach in a paper published in the journal Optica.

    “The ultimate goal of our research is to break the technical barrier imposed on sample thickness and develop a new way of performing 3-D imaging—one that involves mathematically slicing through the sample,” said Xiaojing Huang, a scientist at HXN and a co-author of the paper.

    2
    The research team is pictured at the HXN workstation. Standing, from left to right, are Xiaojing Huang, Hanfei Yan, Evgeny Nazaretski, Yong Chu, Mingyuan Ge, and Zhihua Dong. Sitting, from left to right, are Hande Öztürk and Meifeng Lin. Not pictured: Ian Robinson.

    The conventional method of obtaining a 3-D image involves collecting and combining a series of 2-D images. To obtain these 2-D images, the scientists typically rotate the sample 180 degrees; however, large samples cannot easily rotate within the limited space of typical x-ray microscopes. This limitation, in addition to the challenge of imaging thick samples, makes it nearly impossible to reconstruct a 3-D image with high resolution.

    “Instead of collecting a series of 2-D projections by rotating the sample, we simply ‘slice’ the thick material into a series of thin layers,” said lead author Hande Öztürk. “This slicing process is carried out mathematically without physically modifying the sample.”

    Their technique benefits from HXN’s special optics, called Multilayer Laue lenses (MLLs), which are engineered to focus x-rays into a tiny point. These lenses create favorable conditions for studying thinner slices of thick materials, while also reducing the measurement time.

    “HXN’s unique MLLs have a high focusing efficiency, so we can spend much less time collecting the signal we need,” said Hanfei Yan, a scientist at HXN and a co-author of the paper.

    By combining the MLL optics and the multi-slice approach, the HXN scientists were able to visualize two layers of nanoparticles separated by only 10 microns—about one tenth the diameter of a human hair—and with a resolution 100 times smaller. Additionally, the method significantly cut down the time needed to obtain a single image.

    “This development provides an exciting opportunity to perform 3-D imaging on samples that are very difficult to image with conventional methods—for example, a battery with a complicated electrochemical cell,” said Chu. He added that this approach could be very useful for a wide variety of future research applications.

    This study was supported by Brookhaven Lab’s Laboratory Directed Research and Development program. Operations at NSLS-II are supported by DOE’s 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

    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 1:36 pm on August 17, 2018 Permalink | Reply
    Tags: , BNL, , Photo study   

    From Brookhaven National Laboratory: “The superhot collisions at the Relativistic Heavy Ion Collider ” Photo Study 

    From Brookhaven National Laboratory

    1
    The superhot collisions at the Relativistic Heavy Ion Collider melt protons and neutrons, freeing their inner building blocks, so scientists can study the force that holds them together.

    2
    This new technique literally pushes x-rays to the edge to help draw the nanoworld into greater focus. This rendering shows a high-intensity x-ray beam striking and traveling through an ultra-thin material. The resulting x-ray scattering—those blue and white ripples—is much less distorted than in other methods, which means superior images of nanoscale structures ranging from proteins to catalysts. Get the full story right here: http://1.usa.gov/Y5GY7M

    3
    March 29, 2013 Photo of the Week: Laser Chamber

    This is one of the vacuum chambers where we grow cutting-edge iron-based superconductors that could advance everything from wind turbines to particle accelerators. Our researchers use a technique called pulsed-laser deposition to fabricate superconducting thin films right here– a high-power laser vaporizes materials that are then re-collected in ultra-precise new configurations.

    5
    April 12, 2013 Photo of the Week: Crystal Garden

    Many of the materials we make here at Brookhaven are much too small for traditional tools — good luck trying to hammer atoms into place or screw nanoscale films together. So when we can’t build materials, we grow them.

    The glowing chamber above, an infrared image furnace, is used to grow ultra-precise superconducting crystals. Infrared light focuses onto a rod, melting it at temperatures of about 4,000 degrees Fahrenheit. Under just the right conditions, that liquefied material recrystallizes as a single uniform structure. One of our physicists, Genda Gu, actually pioneered techniques that grow some of the largest single-crystal high-temperature superconductors in the world. And hey, it only takes him a month of gold-assisted gardening to grow each one just right.

    6
    May 3, 2013 Photo of the Week: Tunneling Technology

    The sustainable energy of tomorrow requires custom-designed catalysts to pry power from different fuel sources. To advance this essential technology, our scientists use instruments such as this scanning tunneling microscope to reveal the atomic-scale building blocks and processes that point the way to new breakthroughs.

    Many many more at the full article.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 12:05 pm on August 10, 2018 Permalink | Reply
    Tags: , BNL, , Lining Up the Surprising Behaviors of a Superconductor with One of the World's Strongest Magnets, , , National High Magnetic Field Laboratory, Pulsed Field Facility at Los Alamos National Laboratory,   

    From Brookhaven National Lab: “Lining Up the Surprising Behaviors of a Superconductor with One of the World’s Strongest Magnets” 

    From Brookhaven National Lab

    August 8, 2018

    atantillo@bnl.gov
    Ariana Tantillo
    (631) 344-2347

    Peter Genzer,
    genzer@bnl.gov
    (631) 344-3174

    Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way—a finding that could help direct the search for materials that can perfectly conduct electricity at room temperature.

    1
    (Clockwise from back left) Brookhaven Lab physicists Ivan Bozovic, Anthony Bollinger, and Jie Wu, and postdoctoral researcher Xi He used the molecular beam epitaxy system seen above to synthesize perfect single-crystal thin films made of lanthanum, strontium, oxygen, and copper (LSCO). They brought these superconducting films to the National High Magnetic Field Laboratory to see how the electrical resistance of LSCO in its “strange” metallic state changes under extremely strong magnetic fields.

    What happens when really powerful magnets—capable of producing magnetic fields nearly two million times stronger than Earth’s—are applied to materials that have a “super” ability to conduct electricity when chilled by liquid nitrogen? A team of scientists set out to answer this question in one such superconductor made of the elements lanthanum, strontium, copper, and oxygen (LSCO). They discovered that the electrical resistance of this copper-oxide compound, or cuprate, changes in an unusual way when very high magnetic fields suppress its superconductivity at low temperatures.

    “The most pressing problem in condensed matter physics is understanding the mechanism of superconductivity in cuprates because at ambient pressure they become superconducting at the highest temperature of any currently known material,” said physicist Ivan Bozovic, who leads the Oxide Molecular Beam Epitaxy Group at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and who is a coauthor of the Aug. 3 Science paper reporting the discovery. “This new result—that the electrical resistivity of LSCO scales linearly with magnetic field strength at low temperatures—provides further evidence that high-temperature superconductors do not behave like ordinary metals or superconductors. Once we can come up with a theory to explain their unusual behavior, we will know whether and where to search for superconductors that can carry large amounts of electrical current at higher temperatures, and perhaps even at room temperature.”

    Cuprates such as LSCO are normally insulators. Only when they are cooled to some hundred degrees below zero and the concentrations of their chemical composition are modified (a process called doping) to a make them metallic can their mobile electrons pair up to form a “superfluid” that flows without resistance. Scientists hope that understanding how cuprates achieve this amazing feat will enable them to develop room-temperature superconductors, which would make energy generation and delivery significantly more efficient and less expensive.

    In 2016, Bozovic’s group reported that LSCO’s superconducting state is nothing like the one explained by the generally accepted theory of classical superconductivity; it depends on the number of electron pairs in a given volume rather than the strength of the electron pairing interaction. In a follow-up experiment published the following year, they obtained another puzzling result: when LSCO is in its non-superconducting (normal, or “metallic”) state, its electrons do not behave as a liquid, as would be expected from the standard understanding of metals.

    “The condensed matter physics community has been divided about this most basic question: do the behaviors of cuprates fall within existing theories for superconductors and metals, or are there profoundly different physical principles involved?” said Bozovic.

    Continuing this comprehensive multipart study that began in 2005, Bozovic’s group and collaborators have now found additional evidence to support the latter idea that the existing theories are incomplete. In other words, it is possible that these theories do not encompass every known material. Maybe there are two different types of metals and superconductors, for example.

    “This study points to another property of the strange metallic state in the cuprates that is not typical of metals: linear magnetoresistance at very high magnetic fields,” said Bozovic. “At low temperatures where the superconducting state is suppressed, the electrical resistivity of LSCO scales linearly (in a straight line) with the magnetic field; in metals, this relationship is quadratic (forms a parabola).”

    2
    This composite image offers a glimpse inside the custom-designed molecular beam epitaxy system that the Brookhaven physicists use to create single-crystal thin films for studying the properties of superconducting cuprates.

    In order to study magneto resistance, Bozovic and group members Anthony Bollinger, Xi He, and Jie Wu first had to create flawless single-crystal thin films of LSCO near its optimal doping level. They used a technique called molecular beam epitaxy, in which separate beams containing atoms of the different chemical elements are fired onto a heated single-crystal substrate. When the atoms land on the substrate surface, they condense and slowly grow into ultra-thin layers, building a single atomic layer at a time. The growth of the crystal occurs in highly controlled conditions of ultra-high vacuum to ensure that the samples do not get contaminated.

    “Brookhaven Lab’s key contribution to this study is this material synthesis platform,” said Bozovic. “It allows us to tailor the chemical composition of the films for different studies and provides the foundation for us to observe the true properties of superconducting materials, as opposed to properties induced by sample defects or impurities.”

    The scientists then patterned the thin films onto strips containing voltage leads so that the amount of electrical current flowing through LSCO under an applied magnetic field could be measured.

    They conducted initial magneto resistivity measurements with two 9 Tesla magnets at Brookhaven Lab—for reference, the strength of the magnets used in today’s magnetic resonance imaging (MRI) machines are typically up to 3 Tesla. Then, they brought their best samples (those with the best structural and transport qualities) to the Pulsed Field Facility. Located at DOE’s Los Alamos National Laboratory, this international user facility is part of the National High Magnetic Field Laboratory, which houses some of the strongest magnets in the world. Scientists at the Pulsed Field Facility placed the samples in an 80 Tesla pulsed magnet, powered by quick pulses, or shots, of electrical current. The magnet produces such large magnetic fields that it cannot be energized for more than a very short period of time (microseconds to a fraction of a second) without destroying itself.

    “This large magnet, which is the size of a room and draws the electricity of a small city, is the only such installation on this continent,” said Bozovic. “We only get access to it once a year if we are lucky, so we chose our best samples to study.”

    In October, the scientists will get access to a stronger (90 Tesla) magnet, which they will use to collect additional magneto resistance data to see if the linear relationship still holds.

    3
    An example of a typical device that the scientists use to measure electrical resistivity as a function of temperature and magnetic field. The scientists grew the film via atomic layer-by-layer molecular beam epitaxy, patterned it into a device, and wire bonded it to a chip carrier.

    “While I do not expect to see something different, this higher field strength will allow us to expand the range of doping levels at which we can suppress superconductivity,” said Bozovic. “Collecting more data over a broader range of chemical compositions will help theorists formulate the ultimate theory of high-temperature superconductivity in cuprates.”

    In the next year, Bozovic and the other physicists will collaborate with theorists to interpret the experimental data.

    “It appears that the strongly correlated motion of electrons is behind the linear relationship we observed,” said Bozovic. “There are various ideas of how to explain this behavior, but at this point, I would not single out any of them.”

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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