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  • richardmitnick 3:09 pm on January 16, 2014 Permalink | Reply
    Tags: Advanced Light Source, , , , , , superconductors   

    From Berkeley Lab: “Natural 3D Counterpart to Graphene Discovered” 


    Berkeley Lab

    Researchers at Berkeley Lab’s Advanced Light Source Find New Form of Quantum Matter

    January 16, 2014
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    The discovery of what is essentially a 3D version of graphene – the 2D sheets of carbon through which electrons race at many times the speed at which they move through silicon – promises exciting new things to come for the high-tech industry, including much faster transistors and far more compact hard drives. A collaboration of researchers at the U.S Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered that sodium bismuthate can exist as a form of quantum matter called a three-dimensional topological Dirac semi-metal (3DTDS). This is the first experimental confirmation of 3D Dirac fermions in the interior or bulk of a material, a novel state that was only recently proposed by theorists.

    graph
    A topological Dirac semi-metal state is realized at the critical point in the phase transition from a normal insulator to a topological insulator. The + and – signs denote the even and odd parity of the energy bands.

    “A 3DTDS is a natural three-dimensional counterpart to graphene with similar or even better electron mobility and velocity,” says Yulin Chen, a physicist with Berkeley Lab’s Advanced Light Source (ALS) when he initiated the study that led to this discovery, and now with the University of Oxford. “Because of its 3D Dirac fermions in the bulk, a 3DTDS also features intriguing non-saturating linear magnetoresistance that can be orders of magnitude higher than the materials now used in hard drives, and it opens the door to more efficient optical sensors.”

    Chen is the corresponding author of a paper in Science reporting the discovery. The paper is titled Discovery of a Three-dimensional Topological Dirac Semimetal, Na3Bi. Co-authors were Zhongkai Liu, Bo Zhou, Yi Zhang, Zhijun Wang, Hongming Weng, Dharmalingam Prabhakaran, Sung-Kwan Mo, Zhi-Xun Shen, Zhong Fang, Xi Dai and Zahid Hussain.

    See the full article and all of the excitment here.

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

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  • richardmitnick 3:45 pm on January 15, 2014 Permalink | Reply
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    From Berkeley Lab: “A Deeper Look at Interfaces: Researchers at Berkeley Lab’s Advanced Light Source Develop New Technique for Probing Subsurface Electronic Structure” 


    Berkeley Lab

    January 14, 2014
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    “The interface is the device,” Nobel laureate Herbert Kroemer famously observed, referring to the remarkable properties to be found at the junctures where layers of different materials meet. In today’s burgeoning world of nanotechnology, the interfaces between layers of metal oxides are becoming increasingly prominent, with applications in such high-tech favorites as spintronics, high-temperature superconductors, ferroelectrics and multiferroics. Realizing the vast potential of these metal oxide interfaces, especially those buried in subsurface layers, will require detailed knowledge of their electronic structure.

    group
    From left, Aaron Bostwick, Charles Fadley, Jim Ciston and Alex Gray at the Advanced Light Source’s Beamline 7.0.1. (Photo by Roy Kaltschmidt)

    A new technique from an international team of researchers working at Berkeley Lab’s Advanced Light Source (ALS) promises to deliver the goods. In a study led by Charles Fadley, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California Davis, where he is a Distinguished Professor of Physics, the team combined two well-established techniques for studying electronic structure in crystalline materials into a new technique that is optimized for examining electronic properties at subsurface interfaces. They call this new technique SWARPES, for Standing Wave Angle-Resolved Photoemission Spectroscopy.

    Read all about it. See the full article here.

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  • richardmitnick 6:39 pm on September 16, 2013 Permalink | Reply
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    From Berkeley Lab: “On the Road to Fault-Tolerant Quantum Computing” 


    Berkeley Lab

    Collaboration at Berkeley Lab’s Advanced Light Source Induces High Temperature Superconductivity in a Toplogical Insulator

    September 16, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    Reliable quantum computing would make it possible to solve certain types of extremely complex technological problems millions of times faster than today’s most powerful supercomputers. Other types of problems that quantum computing could tackle would not even be feasible with today’s fastest machines. The key word is “reliable.” If the enormous potential of quantum computing is to be fully realized, scientists must learn to create “fault-tolerant” quantum computers. A small but important step toward this goal has been achieved by an international collaboration of researchers from China’s Tsinghua University and the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) working at the Advanced Light Source (ALS).

    Using premier beams of ultraviolet light at the ALS, a DOE national user facility for synchrotron radiation, the collaboration has reported the first demonstration of high-temperature superconductivity in the surface of a topological insulator – a unique class of advanced materials that are electrically insulating on the inside but conducting on the surface. Inducing high-temperature superconductivity on the surface of a topological insulator opens the door to the creation of a pre-requisite for fault-tolerant quantum computing, a mysterious quasiparticle known as the “Majorana zero mode.”

    “We have shown that by interfacing a topological insulator, bismuth selenide, with a high temperature superconductor, BSCCO (bismuth strontium calcium copper oxide), it is possible to induce superconductivity in the topological surface state,” says Alexei Fedorov, a staff scientist for ALS beamline 12.0.1, where the induced high temperature superconductivity of the topological insulator heterostructure was confirmed. “This is the first reported demonstration of induced high temperature superconductivity in a topological surface state.”

    state
    This schematic of a bismuth selenide/BSCCO cuprate (Bi2212) heterostructure shows a proximity-induced high-temperature superconducting gap on the surface states of the bismuth selenide topological insulator. No image credit.

    See the full article here.

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  • richardmitnick 1:00 pm on August 5, 2013 Permalink | Reply
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    From Berkeley Lab: “3D IR Images Now in Full Color” 


    Berkeley Lab

    Berkeley Lab and University of Wisconsin Researchers Unveil FTIR spectro-microtomography

    August 05, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    “An iconic moment in the history of infrared imaging may have been born with the announcement of the first technique to offer full color IR tomography.

    A collaboration between researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of Wisconsin-Milwaukee (UWM) has combined Fourier Transform Infrared (FTIR) spectroscopy with computed tomography (CT-scans) to create a non-destructive 3D imaging technique that provides molecular-level chemical information of unprecedented detail on biological and other specimens with no need to stain or alter the specimen.

    ‘The notion of having the colors in a 3D reconstructed image being tied to real chemistry is powerful,’ says Michael Martin, an infrared imaging expert at Berkeley Lab’s Advanced Light Source, a DOE national user facility. ‘We’ve all seen pretty 3D renderings of medical scans with colors, for example bone-colored bones, but that’s simply an artistic choice. Now we can spectrally identify the specific types of minerals within a piece of bone and assign a color to each type within the 3D reconstructed image.’

    image
    Researchers at Berkeley Lab and the University of Wisconsin-Milwaukee have reported the first full color infrared tomography. (Image by Cait Youngquist)

    Martin is one of two corresponding authors of a paper describing this research in the journal Nature Methods titled 3D Spectral Imaging with Synchrotron Fourier Transform Infrared Spectro-microtomography. The other corresponding author is UWM physicist Carol Hirschmugl, Director of the Laboratory for Dynamics and Structure at Surfaces and a principal investigator with UW-Madison’s Synchrotron Radiation Center (SRC).”

    mm
    Michael Martin at Berkeley Lab’s Advanced Light Source (Photo by Roy Kaltschmidt, Berkeley Lab)

    woman
    Carol Hirschmugl at University of Wisconsin’s Synchrotron Radiation Center

    See the full article here.

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  • richardmitnick 11:44 am on July 31, 2013 Permalink | Reply
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    From Berkeley Lab: “Berkeley Lab Researchers Discover Universal Law for Light Absorption in 2D Semiconductors” 


    Berkeley Lab

    July 31, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    “From solar cells to optoelectronic sensors to lasers and imaging devices, many of today’s semiconductor technologies hinge upon the absorption of light. Absorption is especially critical for nano-sized structures at the interface between two energy barriers called quantum wells, in which the movement of charge carriers is confined to two-dimensions. Now, for the first time, a simple law of light absorption for 2D semiconductors has been demonstrated.

    Working with ultrathin membranes of the semiconductor indium arsenide, a team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered a quantum unit of photon absorption, which they have dubbed “AQ’,” that should be general to all 2D semiconductors, including compound semiconductors of the III-V family that are favored for solar films and optoelectronic devices. This discovery not only provides new insight into the optical properties of 2D semiconductors and quantum wells, it should also open doors to exotic new optoelectronic and photonic technologies.

    lab
    (From left) Eli Yablonovitch, Ali Javey and Hui Fang discovered a simple law of light absorption for 2D semiconductors that should open doors to exotic new optoelectronic and photonic technologies. (Photo by Roy Kaltschmidt)

    ‘We used free-standing indium arsenide membranes down to three nanometers in thickness as a model material system to accurately probe the absorption properties of 2D semiconductors as a function of membrane thickness and electron band structure,’ says Ali Javey, a faculty scientist in Berkeley Lab’s Materials Sciences Division and a professor of electrical engineering and computer science at the University of California (UC) Berkeley. ‘We discovered that the magnitude of step-wise absorptance in these materials is independent of thickness and band structure details.’”

    ia
    Indium arsenide is a III–V semiconductor with electron mobility and velocity that make it an outstanding candidate for future high-speed, low-power opto-electronic devices.

    See the full article here.

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  • richardmitnick 12:26 pm on June 28, 2013 Permalink | Reply
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    From Berkeley Lab: “This Image Could Lead to Better Antibiotics” 


    Berkeley Lab

    Berkeley Lab scientists create atomic-scale structure of ribosome attached to a molecule that controls its motion.

    June 27, 2013
    Dan Krotz

    “This may look like a tangle of squiggly lines, but you’re actually looking at a molecular machine called a ribosome. Its job is to translate DNA sequences into proteins, the workhorse compounds that sustain you and all living things.

    ribo

    The image is also a milestone. It’s the first time the atom-by-atom structure of the ribosome has been seen as it’s attached to a molecule that controls its motion. That’s big news if you’re a structural biologist.

    But there’s another way to look at this image, one that anyone who’s suffered a bacterial infection can appreciate. The image is also a roadmap to better antibiotics. That’s because this particular ribosome is from a bacterium. And somewhere in its twists and turns could be a weakness that a new antibiotic can target.

    ‘We’re in an arms race with the resistance mechanisms of bacteria,’ says Jamie Cate, a staff scientist in Berkeley Lab’s Physical Biosciences Division and a professor of biochemistry, biophysics and structural biology at UC Berkeley.

    ‘The better we understand how bacterial ribosomes work, the better we can come up with new ways to interfere with them,’ he adds.

    Cate developed the structure with UC Berkeley’s Arto Pulk. Their work is described in the June 28 issue of the journal Science.

    ws
    Here’s the kind of equipment required to create that image. This is the endstation of an Advanced Light Source beamline called SIBYLS, or Structurally Integrated Biology for Life Sciences.

    Cate and Pulk used protein crystallography beamlines at Berkeley Lab’s Advanced Light Source to create diffraction patterns that show how the ribosome’s molecules fit together. They then used computational modeling to combine these patterns into incredibly high-resolution images that describe the locations of the individual atoms.”

    See the full article here.

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

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  • richardmitnick 1:23 pm on May 22, 2013 Permalink | Reply
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    From Berkeley Lab: “Whirlpools on the Nanoscale Could Multiply Magnetic Memory” 


    Berkeley Lab

    At the Advanced Light Source, Berkeley Lab scientists join an international team to control spin orientation in magnetic nanodisks

    May 21, 2013
    Paul Preuss 510-486-6249 paul_preuss@lbl.gov

    ‘We spent 15 percent of home energy on gadgets in 2009, and we’re buying more gadgets all the time,’ says Peter Fischer of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). Fischer lets you know right away that while it’s scientific curiosity that inspires his research at the Lab’s Advanced Light Source (ALS), he intends it to help solve pressing problems.

    graph
    The electron spins in a magnetic vortex all point in parallel, either clockwise or counterclockwise. Spins in the crowded core of the vortex must point out of the plane, either up or down. The four orientations of circularity and polarity could form the cells of multibit magnetic storage and processing systems.

    ‘What we’re working on now could make these gadgets perform hundreds of times better and also be a hundred times more energy efficient,’ says Fischer, a staff scientist in the Materials Sciences Division. As a principal investigator at the Center for X-Ray Optics, he leads ALS beamline 6.1.2, where he specializes in studies of magnetism.

    Fischer recently provided critical support to a team led by Vojtĕch Uhlíř of the Brno University of Technology in the Czech Republic and the Center for Magnetic Recording Research at the University of California, San Diego. Researchers from both institutions and from Berkeley Lab used the unique capabilities of beamline 6.1.2 to advance a new concept in magnetic memory.

    ‘Magnetic memory is at the heart of most electronic devices,’ says Fischer, ‘and from the scientist’s point of view, magnetism is about controlling electron spin.’

    Magnetic memories store bits of information in discrete units whose electron spins all line up in parallel, pointing one way or the opposite to signify a one or a zero. What Fischer and his colleagues propose is multibit storage in which each unit has four states instead of two and can store twice the information.

    See the full article here. This may effect a lot of what you do.

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

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  • richardmitnick 10:58 am on March 13, 2013 Permalink | Reply
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    From Berkeley Lab: “Surprising Control over Photoelectrons from a Topological Insulator” 


    Berkeley Lab

    Berkeley Lab scientists discover how a photon beam can flip the spin polarization of electrons emitted from an exciting new material

    Plain-looking but inherently strange crystalline materials called 3D topological insulators (TIs) are all the rage in materials science. Even at room temperature, a single chunk of TI is a good insulator in the bulk, yet behaves like a metal on its surface.

    block
    The interior bulk of a topological insulator is indeed an insulator, but electrons (spheres) move swiftly on the surface as if through a metal. They are spin-polarized, however, with their momenta (directional ribbons) and spins (arrows) locked together. Berkeley Lab researchers have discovered that the spin polarization of photoelectrons (arrowed sphere at upper right) emitted when the material is struck with high-energy photons (blue-green waves from left) is completely determined by the polarization of this incident light. (Image Chris Jozwiak, Zina Deretsky, and Berkeley Lab Creative Services Office)

    Researchers find TIs exciting partly because the electrons that flow swiftly across their surfaces are ‘spin polarized': the electron’s spin is locked to its momentum, perpendicular to the direction of travel. These interesting electronic states promise many uses – some exotic, like observing never-before-seen fundamental particles, but many practical, including building more versatile and efficient high-tech gadgets, or, further into the future, platforms for quantum computing.

    A team of researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley has just widened the vista of possibilities with an unexpected discovery about TIs: when hit with a laser beam, the spin polarization of the electrons they emit (in a process called photoemission) can be completely controlled in three dimensions, simply by tuning the polarization of the incident light.

    ‘The first time I saw this it was a shock; it was such a large effect and was counter to what most researchers had assumed about photoemission from topological insulators, or any other material,’ says Chris Jozwiak of Berkeley Lab’s Advanced Light Source (ALS), who worked on the experiment. ‘Being able to control the interaction of polarized light and photoelectron spin opens a playground of possibilities.’”

    See the full article here.

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  • richardmitnick 6:16 pm on March 3, 2013 Permalink | Reply
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    From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe” 


    Berkeley Lab

    Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

    February 20, 2013
    Paul Preuss

    “By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

    isotopes
    The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today.

    In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

    ‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

    At this point, I direct you to the full article. There is a lot going on here.

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

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  • richardmitnick 8:20 pm on December 13, 2012 Permalink | Reply
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    From Berkeley Lab: “Nanocrystals Not Small Enough to Avoid Defects” 


    Berkeley Lab

    Berkeley Lab Scientists at Advanced Light Source Show Dislocations Can Be Induced by Pressure in Ultrafine Nanocrystals

    als
    Interior of the ALS at Berkeley Lab

    December 13, 2012
    Lynn Yarris

    “Nanocrystals as protective coatings for advanced gas turbine and jet engines are receiving a lot of attention for their many advantageous mechanical properties, including their resistance to stress. However, contrary to computer simulations, the tiny size of nanocrystals apparently does not safeguard them from defects.

    nnc
    Stress-induced deformation of nanocrystalline nickel reflects the dislocation activity observed by researchers at Berkeley Lab’s Advanced Light Source using a radial diamond-anvil-cell X-ray diffraction experimental station. (Image courtesy of NDT Education Resource Center)

    daw
    A radial diamond-anvil-cell allows for in situ X-ray diffraction experiments at superbend beamline 12.2.2 of Berkeley Lab’s Advanced Light Source. (Photo by Roy Kaltschmidt)

    In a study by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab)and collaborators from multiple institutions, nanocrystals of nickel subjected to high pressure continued to suffer dislocation-mediated plastic deformation even when the crystals were only three nanometers in size. These experimental findings, which were carried out at Berkeley Lab’s Advanced Light Source (ALS), a premier source of X-rays and ultraviolet light for scientific research, show that dislocations can form in the finest of nanocrystals when stress is applied.

    ‘We cannot ignore or underestimate the role of dislocations – defects or irregularities – in fine nanocrystals as external stress can change the entire picture,’ says Bin Chen, a materials scientist with the ALS Experimental Systems Group who led this research. ‘Our results demonstrate that dislocation-mediated deformation persists to smaller crystal sizes than anticipated, primarily because computer models have not given enough consideration to the effects of external stress and grain boundaries.’”

    See the full article here.

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

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