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  • richardmitnick 9:09 am on August 15, 2014 Permalink | Reply
    Tags: , , Condensed Matter Physics, Superconductivity   

    From Brookhaven Lab: “New Grant to Aid Search for the Secrets of Superconductivity” 

    Brookhaven Lab

    August 12, 2014
    Karen McNulty Walsh

    Research aimed at unlocking the secrets of high-temperature superconductivity at the U.S. Department of Energy’s Brookhaven National Laboratory will get a boost from a new grant awarded to Ivan Bozovic, a Brookhaven physicist and an Adjunct Professor at Yale University, by the Gordon and Betty Moore Foundation. Bozovic will receive $1.9 million over five years as part of the Moore Materials Synthesis Investigators program to continue the meticulous assembly and manipulation of superconducting thin films and the exploration of factors underlying these remarkable materials’ ability to carry electric current with no energy loss.

    “I am very grateful for this grant, which recognizes the importance of methodical work that slowly but steadily improves materials synthesis techniques and sample quality,” Bozovic said. Such quality is essential to uncover subtle effects in high-temperature superconductors, which, Bozovic notes, can be masked by impurities. “The better the samples, the more precise and revealing our experiments can be — and the greater their potential for new insights and discoveries,” he said.

    To achieve such precision, Bozovic uses a one-of-a-kind molecular-beam epitaxy (MBE) machine that he built and continues to improve to fabricate superconducting thin films one atomic layer at a time. He and collaborators have used the machine to assemble more than 2,000 thin film samples and conduct hundreds of scientific experiments. He also contributes to research at Brookhaven’s Center for Emergent Superconductivity, one of DOE’s Energy Frontier Research Centers, which recently received renewed funding.

    “I am very grateful for this grant, which recognizes the importance of methodical work that slowly but steadily improves materials synthesis techniques and sample quality.”
    — Brookhaven physicist Ivan Bozovic

    ib

    Leveraging his atomic-layer-by-layer synthesis technique, Bozovic made a series of discoveries related to interface superconductivity, bringing it to the forefront of research in Condensed Matter Physics. He showed that superfluid can be confined to a single atomic layer at the interface of two materials, neither of which is superconducting. In another important experiment, he proved that electron pairs exist on both sides of the superconductor-to-insulator transition an important insight into the mysterious nature of the high-temperature superconductivity phenomenon.

    Bozovic is one of only 12 scientists to be awarded funding through the Moore Materials Synthesis Investigators program, part of the foundation’s Emerging Phenomena in Quantum Systems (EPiQS) initiative. Quantum materials, the Foundation notes, are substances in which the collective behavior of electrons leads to many complex and unexpected emergent phenomena, superconductivity being a prominent example.

    In announcing the grantees, the Foundation stated:

    “Our approach is to focus on some of the field’s leading scientists; to allow these scientists the freedom to explore and the flexibility to change research directions; and to incentivize sample sharing within the EPiQS program and beyond…We believe that our programs will lead to discoveries of new quantum materials with emergent electronic properties as well as an increase in the availability of top-quality samples to the experimental community.”

    Bozovic earned a Ph.D. in physics from the University of Belgrade in Yugoslavia in 1975. He remained there until 1985 and served as a professor and the Head of the Physics Department. From 1986 until 1988, he worked at the Applied Physics Department at Stanford University. He was a senior research scientist at Varian Research Center in Palo Alto, California, 1989 to 1998, and the chief technical officer and principal scientist for Oxxel GmbH in Germany 1998 to 2002. He joined Brookhaven as a senior scientist and the leader of the Molecular Beam Epitaxy group in 2003. In 2012 he was a co-recipient of the Bernd T. Matthias Prize for Superconducting Materials, and in 2013 was chosen to give the Max Planck Lecture at MPI-Stuttgart, Germany. His research results have been published in more than 200 research papers and cited more than 6,500 times. Many of these were published in the highest-impact journals such as Nature, Science, and Nature Materials. Bozovic is a Fellow of APS and of SPIE, and a Foreign Member of Serbian Academy of Science and Arts.

    Bozovic’s research at Brookhaven is supported by the DOE Office of Science. The Moore Foundation grant will be awarded to him by way of his adjunct appointment at Yale University.

    See the full article here.

    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 6:07 pm on February 13, 2014 Permalink | Reply
    Tags: , , , , , Superconductivity   

    From Brookhaven Lab: “Superconductivity in Orbit: Scientists Find New Path to Loss-Free Electricity” 

    Brookhaven Lab

    February 13, 2014
    Contacts: Justin Eure, (631) 344-2347 or Peter Genzer, (631) 344-3174

    Brookhaven Lab researchers captured the distribution of multiple orbital electrons to help explain the emergence of superconductivity in iron-based materials

    Armed with just the right atomic arrangements, superconductors allow electricity to flow without loss and radically enhance energy generation, delivery, and storage. Scientists tweak these superconductor recipes by swapping out elements or manipulating the valence electrons in an atom’s outermost orbital shell to strike the perfect conductive balance. Most high-temperature superconductors contain atoms with only one orbital impacting performance—but what about mixing those elements with more complex configurations?

    four
    Brookhaven Lab scientists and study coauthors (from left) Lijun Wu, Yimei Zhu, Chris Homes, and Weiguo Yin stand by the electron microscope used to reveal the multi-orbital distributions with a technique called quantitative convergent beam electron diffraction (CBED).

    Now, researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have combined atoms with multiple orbitals and precisely pinned down their electron distributions. Using advanced electron diffraction techniques, the scientists discovered that orbital fluctuations in iron-based compounds induce strongly coupled polarizations that can enhance electron pairing—the essential mechanism behind superconductivity. The study, set to publish soon in the journal Physical Review Letters, provides a breakthrough method for exploring and improving superconductivity in a wide range of new materials.

    “For the first time, we obtained direct experimental evidence of the subtle changes in electron orbitals by comparing an unaltered, non-superconducting material with its doped, superconducting twin,” said Brookhaven Lab physicist and project leader Yimei Zhu.

    While the effect of doping the multi-orbital barium iron arsenic—customizing its crucial outer electron count by adding cobalt—mirrors the emergence of high-temperature superconductivity in simpler systems, the mechanism itself may be entirely different.

    “Now superconductor theory can incorporate proof of strong coupling between iron and arsenic in these dense electron cloud interactions,” said Brookhaven Lab physicist and study coauthor Weiguo Yin. “This unexpected discovery brings together both orbital fluctuation theory and the 50-year-old ‘excitonic’ theory for high-temperature superconductivity, opening a new frontier for condensed matter physics.”

    Atomic Jungle Gym

    Imagine a child playing inside a jungle gym, weaving through holes in the multicolored metal matrix in much the same way that electricity flows through materials. This particular kid happens to be wearing a powerful magnetic belt that repels the metal bars as she climbs. This causes the jungle gym’s grid-like structure to transform into an open tunnel, allowing the child to slide along effortlessly. The real bonus, however, is that this action attracts any nearby belt-wearing children, who can then blaze through that perfect path.

    two
    These images show the distribution of the valence electrons in the samples explored by the Brookhaven Lab collaboration—both feature a central iron layer sandwiched between arsenic atoms. The tiny red clouds (more electrons) in the undoped sample on the left (BaFe2As2) reveal the weak charge quadrupole of the iron atom, while the blue clouds (fewer electrons) around the outer arsenic ions show weak polarization. The superconducting sample on the right (doped with cobalt atoms), however, exhibits a strong quadrupole in the center and the pronounced polarization of the arsenic atoms, as evidenced by the large, red balloons.

    Flowing electricity can have a similar effect on the atomic lattices of superconductors, repelling the negatively charged valence electrons in the surrounding atoms. In the right material, that repulsion actually creates a positively charged pocket, drawing in other electrons as part of the pairing mechanism that enables the loss-free flow of current—the so-called excitonic mechanism. To design an atomic jungle gym that warps just enough to form a channel, scientists audition different combinations of elements and tweak their quantum properties.

    “High-temperature copper-oxide superconductors, or cuprates, contain in effect a single orbital and lack the degree of freedom to accommodate strong enough interactions between electricity and the lattice,” Yin said. “But the barium iron arsenic we tested has multi-orbital electrons that push and pull the lattice in much more flexible and complex ways, for example by inter-orbital electron redistribution. This feature is especially promising because electricity can shift arsenic’s electron cloud much more easily than oxygen’s.”

    In the case of the atomic jungle gym, this complexity demands new theoretical models and experimental data, considering that even a simple lattice made of north-south bar magnets can become a multidimensional dance of attraction and repulsion. To control the doping effects and flow of electricity, scientists needed a window into the orbital interactions.

    Tracking Orbits

    “Consider measuring waves crashing across the ocean’s surface,” Zhu said. “We needed to pinpoint those complex fluctuations without having the data obscured by the deep water underneath. The waves represent the all-important electrons in the outer orbital shells, which are barely distinguishable from the layers of inner electrons. For example, each barium atom alone has 56 electrons, but we’re only concerned with the two in the outermost layer.”

    The Brookhaven researchers used a technique called quantitative convergent beam electron diffraction (CBED) to reveal the orbital clouds with subatomic precision. After an electron beam strikes the sample, it bounces off the charged particles to reveal the configuration of the atomic lattice, or the exact arrays of nuclei orbited by electrons. The scientists took thousands of these measurements, subtracted the inner electrons, and converted the data into probabilities—balloon-shaped areas where the valence electrons were most likely to be found.

    Shape-Shifting Atoms

    The researchers first examined the electron clouds of non-superconducting samples of barium iron arsenic. The CBED data revealed that the arsenic atoms—placed above and below the iron in a sandwich-like shape (see image)—exhibited little shift or polarization of valence electrons. However, when the scientists transformed the compound into a superconductor by doping it with cobalt, the electron distribution radically changed.

    “Cobalt doping pushed the orbital electrons in the arsenic outward, concentrating the negative charge on the outside of the ‘sandwich’ and creating a positively charged pocket closer to the central layer of iron,” Zhu said. “We created very precise electronic and atomic displacement that might actually drive the critical temperature of these superconductors higher.”

    Added Yin, “What’s really exciting is that this electron polarization exhibits strong coupling. The quadrupole polarization of the iron, which indicates the orbital fluctuation, couples intimately with the arsenic dipole polarization—this mechanism may be key to the emergence of high-temperature superconductivity in these iron-based compounds. And our results may guide the design of new materials.”

    This study explored the orbital fluctuations at room temperature under static conditions, but future experiments will apply dynamic diffraction methods to super-cold samples and explore alternative material compositions.

    The experimental work at Brookhaven Lab was supported by DOE’s Office of Science. The materials synthesis was carried out at the Chinese Academy of Sciences’ Institute of Physics. Brookhaven Lab coauthors of the study also include Chao Ma, Lijun Wu, and Chris Homes.

    See the full article here.

    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 6:35 pm on November 18, 2013 Permalink | Reply
    Tags: , , , , Superconductivity   

    From Berkeley Lab: “A Superconductor-Surrogate Earns Its Stripes” 


    Berkeley Lab

    November 18, 2013
    Berkeley Lab Study Reveals Origins of an Exotic Phase of Matter

    Alison Hatt 510-486-7154 ajhatt@lbl.gov

    Understanding superconductivity – whereby certain materials can conduct electricity without any loss of energy – has proved to be one of the most persistent problems in modern physics. Scientists have struggled for decades to develop a cohesive theory of superconductivity, largely spurred by the game-changing prospect of creating a superconductor that works at room temperature, but it has proved to be a tremendous tangle of complex physics.

    Now scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have teased out another important tangle from this giant ball of string, bringing us a significant step closer to understanding how high- temperature superconductors work their magic. Working with a model compound, the team illuminated the origins of the so-called “stripe phase” in which electrons become concentrated in stripes throughout a material, and which appears to be linked to superconductivity.

    image
    Ultrafast changes in the optical properties of strontium-doped lanthanum nickelate throughout the infrared spectrum expose a rapid dynamics of electronic localization in the nickel-oxide plane, shown at left. This process, illustrated on the right, comprises the first step in the formation of ordered charge patterns or “stripes.”

    “We’re trying to understand nanoscale order and how that determines material properties such as superconductivity,” said Robert Kaindl, a physicist in Berkeley Lab’s Materials Sciences Division. “Using ultrafast optical techniques, we are able to observe how charge stripes start to form on a time scale of hundreds of femtoseconds.” A femtosecond is just one millionth of one billionth of a second.

    Electrons in a solid material interact extremely quickly and on very short length scales, so to observe their behavior researchers have built extraordinarily powerful “microscopes” that zoom into fast events using short flashes of laser light. Kaindl and his team brought to bear the power of their ultrafast-optics expertise to understand the stripe phase in strontium-doped lanthanum nickelate (LSNO), a close cousin of high-temperature superconducting materials.

    “We chose to work with LSNO because it has essential similarities to the cuprates (an important class of high-temperature superconductors), but its lack of superconductivity lets us focus on understanding just the stripe phase,” said Giacomo Coslovich, a postdoctoral researcher at Berkeley Lab working with Kaindl.

    “With science, you have to simplify your problems,” Coslovich continued. “If you try to solve them all at once with their complicated interplay, you will never understand what’s going on.”

    two
    Giacomo Coslovich (left) and Robert Kaindl (right) next to the laser setup that generates extremely short pulses of light at “mid-infrared” wavelengths, far beyond the spectrum perceptible by the human eye.

    Beyond the ultrafast measurements, the team also studied X-ray scattering and the infrared reflectance of the material at the neighboring Advanced Light Source, to develop a thorough, cohesive understanding of the stripe phase and why it forms.

    Said Kaindl, “We took advantage of our fortunate location in the national lab environment, where we have both these ultrafast techniques and the Advanced Light Source. This collaborative effort made this work possible.”

    See the full article here.

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

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  • richardmitnick 12:47 pm on October 18, 2013 Permalink | Reply
    Tags: , , , , Superconductivity   

    From Brookhaven Lab: “A Grand Unified Theory of Exotic Superconductivity? 

    Brookhaven Lab

    October 17, 2013
    Contacts: Karen McNulty Walsh, (631) 344-8350 or Peter Genzer, (631) 344-3174

    Scientists introduce a general theoretical approach that describes all known forms of high-temperature superconductivity and their “intertwined” phases

    Years of experiments on various types of high-temperature (high-Tc) superconductors—materials that offer hope for energy-saving applications such as zero-loss electrical power lines—have turned up an amazing array of complex behaviors among the electrons that in some instances pair up to carry current with no resistance, and in others stop the flow of current in its tracks. The variety of these exotic electronic phenomena is a key reason it has been so hard to identify unifying concepts to explain why high-Tc superconductivity occurs in these promising materials.

    sd
    Séamus Davis

    Now Séamus Davis, a physicist who’s conducted experiments on many of these materials at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Cornell University, and Dung-Hai Lee, a theorist at DOE’s Lawrence Berkeley National Laboratory and the University of California, Berkeley, postulate a set of key principles for understanding the superconductivity and the variety of “intertwined” electronic phenomena that applies to all the families of high-Tc superconductors. They describe these general concepts in a paper published in the Proceedings of the National Academy of Sciences October 10, 2013.

    “If we are right, this is kind of the ‘light at the end of the tunnel’ point,” said Davis. “After decades of wondering which are the key things we need to understand high-Tc superconductivity and which are the peripheral things, we think we have identified what the essential elements are.”

    Said Lee, “The next step is to be able to predict which other materials will have these essential elements that will drive high Tc superconductivity—and that ability is still under development.”

    See the full article here.

    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 7:32 pm on August 4, 2013 Permalink | Reply
    Tags: , , , , , Superconductivity,   

    From Brookhaven Lab: “Scientists Discover Hidden Magnetic Waves in High-Temperature Superconductors” 

    Brookhaven Lab

    Advanced x-ray technique reveals surprising quantum excitations that persist through materials with or without superconductivity

    August 4, 2013
    Contacts: Justin Eure, (631) 344-2347 or Peter Genzer, (631) 344-3174

    “Intrinsic inefficiencies plague current systems for the generation and delivery of electricity, with significant energy lost in transit. High-temperature superconductors (HTS)—uniquely capable of transmitting electricity with zero loss when chilled to subzero temperatures—could revolutionize the planet’s aging and imperfect energy infrastructure, but the remarkable materials remain fundamentally puzzling to physicists. To unlock the true potential of HTS technology, scientists must navigate a quantum-scale labyrinth and pin down the phenomenon’s source.

    Now, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and other collaborating institutions have discovered a surprising twist in the magnetic properties of HTS, challenging some of the leading theories. In a new study, published online in the journal Nature Materials on August 4, 2013, scientists found that unexpected magnetic excitations—quantum waves believed by many to regulate HTS—exist in both non-superconducting and superconducting materials.

    four men
    Brookhaven Lab scientists (from left) Ivan Bozovic, Yujie Sun, Mark Dean, and John Hill stand in front of an x-ray diffractometer used to check the structural quality of the custom-grown materials, confirming that they were near-perfect crystals with atomically smooth surfaces before being taken to the European Synchrotron Radiation Facility.

    ‘This is a major experimental clue about which magnetic excitations are important for high-temperature superconductivity,’ said Mark Dean, a physicist at Brookhaven Lab and lead author on the new paper. ‘Cutting-edge x-ray scattering techniques allowed us to see excitations in samples previously thought to be essentially non-magnetic.’

    Perfectly Dope

    Superconductivity demands extremely cold conditions and a precise chemical recipe. Beyond selecting the right elements from the periodic table, physicists carefully tweak the electron content of atoms through a process called doping. Doping determines the average number of electrons present in each atom, and in turn dictates both the behavior of spin waves and the presence of HTS, which emerges around a particular doping sweet spot.

    For this study, the team examined thin films of lanthanum, strontium, copper, and oxygen—often abbreviated as LSCO. These particular HTS materials can be tuned to exhibit a wide range of different electronic behaviors.
    ‘This is the only system that lets us examine the entire phase diagram, from a strongly correlated insulator all the way to a non-superconducting metal,” said Brookhaven physicist John Hill, coauthor on the paper. “We could measure magnetic excitations both before and after the ideal doping levels for superconductivity.’

    ‘Discovering excitations that do not depend on doping levels means that the relationship between high-temperature superconductivity and the waves in these films is more intricate than we suspected.’— Physicist John Hill.

    Measuring a Quantum Sea

    The quantum ripples themselves have wavelengths measured on the Ångstrom scale—smaller than one billionth of a meter. To detect these tiny fluctuations, the scientists applied a technique called resonant inelastic x-ray scattering (RIXS) to the full range of LSCO films. The measurements were taken with the Advanced X-ray Emission Spectrometer at the European Synchrotron Radiation Facility (ESRF) in France. The design, construction, and commissioning of this instrument was led by Giacomo Ghiringhelli and Lucio Braicovich at the Politecnico di Milano in Italy and by Nick Brookes at the ESRF. The Brookhaven Lab team worked in close collaboration with these scientists to perform the RIXS measurements.

    See the full article here.

    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 2:36 pm on July 16, 2013 Permalink | Reply
    Tags: , , , , Superconductivity   

    From Brookhaven Lab: “Imaging Electron Pairing in a Simple Magnetic Superconductor” 

    Brookhaven Lab

    Findings and resulting theory could reveal mechanism behind zero-energy-loss current-carrying capability

    July 14, 2013
    Contacts: Karen McNulty Walsh, (631) 344-8350 or Peter Genzer, (631) 344-3174

    “In the search for understanding how some magnetic materials can be transformed to carry electric current with no energy loss, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory, Cornell University, and collaborators have made an important advance: Using an experimental technique they developed to measure the energy required for electrons to pair up and how that energy varies with direction, they’ve identified the factors needed for magnetically mediated superconductivity—as well as those that aren’t.

    ‘Our measurements distinguish energy levels as small as one ten-thousandth the energy of a single photon of light—an unprecedented level of precision for electronic matter visualization,’ said Séamus Davis, Senior Physicist at Brookhaven the J.G. White Distinguished Professor of Physical Sciences at Cornell, who led the research described in Nature Physics. ‘This precision was essential to writing down the mathematical equations of a theory that should help us discover the mechanism of magnetic superconductivity, and make it possible to search for or design materials for zero-loss energy applications.’

    The material Davis and his collaborators studied was discovered in part by Brookhaven physicist Cedomir Petrovic ten years ago, when he was a graduate student working at the National High Magnetic Field Laboratory. It’s a compound of cerium, cobalt, and indium that many believe may be the simplest form of an unconventional superconductor—one that doesn’t rely on vibrations of its crystal lattice to pair up current-carrying electrons. Unlike conventional superconductors employing that mechanism, which must be chilled to near absolute zero (-273 degrees Celsius) to operate, many unconventional superconductors operate at higher temperatures—as high as -130°C. Figuring out what makes electrons pair in these so-called high-temperature superconductors could one day lead to room-temperature varieties that would transform our energy landscape.

    ‘Scientists have thought this material might be the one, a compound that would give us access to the fundamentals of magnetic superconductivity in a controllable way,’ Davis said. ‘But we didn’t have the tools to directly study the process of electron pairing. This paper announces the successful invention of the techniques and the first examination of how that material works to form a magnetic superconductor.'”

    image
    The height above the plane of this diagram represents the energy required to break a superconducting pair of electrons into separate heavy fermions traveling in different directions (as determined from the quasiparticle scattering patterns). The maximum height is at the locations predicted if the “glue” holding the electron pairs together is magnetism. No image credit.

    See thew full article here.

    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 11:03 am on June 21, 2013 Permalink | Reply
    Tags: , , , , Superconductivity   

    From Argonne Lab: “A Further Understanding of Superconductivity” 

    Argonne National Laboratory

    JUNE 10, 2013
    No Writer Credit

    “A crucial ingredient of high-temperature superconductivity can be found in a class of materials that is entirely different than conventional superconductors. That discovery is the result of research by an international team of scientists working at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS).

    ‘There have been more than 60,000 papers published on high-temperature superconductive material since its discovery in 1986, said Jak Chakhalian, professor of physics at the University of Arkansas (UA) and a co-author of a new paper published on May 13, 2013, in Scientific Reports. ‘Unfortunately, as of today we have zero theoretical understanding of the mechanism behind this enigmatic phenomenon. In my mind, high-temperature superconductivity is the most important unsolved mystery of condensed matter physics.’

    Superconductivity is a phenomenon that occurs in certain materials when cooled to extremely low temperatures such as -435° F. High temperature superconductivity occurs above -396 F, and has been seen up to -218 F in HgBa2Ca2Cu3O8. In both cases, electrical resistance drops to zero and complete expulsion of magnetic fields occurs.

    sc
    The entire crystal structure of the chemical compound CaCu3Cr4O12, an A-site ordered perovskite.No image credit.

    Because superconductors have the ability to transport large electrical currents and produce high magnetic fields, they have long held great potential for electronic devices and power transmission.”

    See the full article here.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

    Argonne APS
    Argonne APS Campus

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science
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  • richardmitnick 4:03 pm on February 24, 2013 Permalink | Reply
    Tags: , , Superconductivity   

    From Brookhaven Lab: “Laser Mastery Narrows Down Sources of Superconductivity” 

    Brookhaven Lab

    MIT and Brookhaven Lab physicists measured fleeting electron waves to uncover the elusive mechanism behind high-temperature superconductivity

    February 24, 2013
    Contacts: Justin Eure or Peter Genzer

    Identifying the mysterious mechanism underlying high-temperature superconductivity (HTS) remains one of the most important and tantalizing puzzles in physics. This remarkable phenomenon allows electric current to pass with perfect efficiency through materials chilled to subzero temperatures, and it may play an essential role in revolutionizing the entire electricity chain, from generation to transmission and grid-scale storage. Pinning down one of the possible explanations for HTS—fleeting fluctuations called charge-density waves (CDWs)—could help solve the mystery and pave the way for rapid technological advances.

    lab
    Inside a clean room, Brookhaven physicists Ivan Bozovic(left) and Anthony Bollinger work on the molecular beam epitaxy system that produced the atomically perfect materials used in the study.

    Now, researchers at the Massachusetts Institute of Technology and the U.S. Department of Energy’s Brookhaven National Laboratory have combined two state-of-the-art experimental techniques to study those electron waves with unprecedented precision in two-dimensional, custom-grown materials. The surprising results, published online February 24, 2013, in the journal Nature Materials, reveal that CDWs cannot be the root cause of the unparalleled power conveyance in HTS materials. In fact, CDW formation is an independent and likely competing instability.

    ‘It has been difficult to determine whether or not dynamic or fluctuating CDWs even exist in HTS materials, much less identify their role,’ said Brookhaven Lab physicist and study coauthor Ivan Bozovic. ‘Do they compete with the HTS state, or are they perhaps the very essence of the phenomenon? That question has now been answered by targeted experimentation.’”

    See the full article to learn what the researchers discovered.

    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 2:06 pm on February 18, 2013 Permalink | Reply
    Tags: , , , , , Superconductivity   

    From Brookhaven Lab: “Dopants Dramatically Alter Electronic Structure of Superconductor” 

    Brookhaven Lab

    Findings explain unusual properties, but complicate search for universal theory.

    February 17, 2013
    No Writer Credit

    “Over the last quarter century, scientists have discovered a handful of materials that can be converted from magnetic insulators or metals into ‘superconductors‘ able to carry electrical current with no energy loss—an enormously promising idea for new types of zero-resistance electronics and energy-storage and transmission systems. At present, a key step to achieving superconductivity (in addition to keeping the materials very cold) is to substitute a different kind of atom into some positions of the ‘parent’ material’s crystal framework. Until now, scientists thought this process, called doping, simply added more electrons or other charge carriers, thereby rendering the electronic environment more conducive to the formation of electron pairs that could move with no energy loss if the material is held at a certain chilly temperature.

    dopants
    Scientists have found that the substitution of cobalt atoms into the crystal framework of an iron-based material—which is required to convert the material from a magnet into a superconductor—also introduces elongated impurity states at each cobalt atom (note the directional alignment of “twin” peaks around each cobalt atom in the electronic structure map). These elongated impurities then scatter electrons in an asymmetric way that explains many of the material’s unusual properties, and could eventually lead to the design of new types of superconductors for practical applications in energy transmission and storage.

    Now, new studies of an iron-based superconductor by an international team of scientists—including physicists from the U.S. Department of Energy’s Brookhaven National Laboratory and Cornell University—suggest that the story is somewhat more complicated. Their research, published online in Nature Physics February 17, 2013, demonstrates that doping, in addition to adding electrons, dramatically alters the atomic-scale electronic structure of the parent material, with important consequences for the behavior of the current-carrying electrons.

    ‘The key observation—that dopant atoms introduce elongated impurity states which scatter electrons in the material in an asymmetric way—helps explain most of the unusual properties, said J.C. Séamus Davis, the study’s lead author, who directs the Center for Emergent Superconductivity at Brookhaven Lab and is also the J.G. White Distinguished Professor of Physical Sciences at Cornell University. ‘Our findings provide a new starting point for theorists trying to grapple with how these materials work, and could potentially point to new ways to design superconductors with improved properties,’ he said.

    JCS
    J.C. Séamus Davis (photo courtesy of Cornell University)

    See the full article here.

    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. 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


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  • richardmitnick 9:01 pm on February 16, 2013 Permalink | Reply
    Tags: , , Superconductivity   

    From Argonne: “Vortex pinning could lead to superconducting breakthroughs” 

    News from Argonne National Laboratory

    February 12, 2013
    Louise Lerner

    A team of researchers from Russia, Spain, Belgium, the U.K. and the U.S. Department of Energy’s (DOE) Argonne National Laboratory announced findings last week that may represent a breakthrough in applications of superconductivity.

    vortex
    This mosaic represents the distribution of superconductivity around holes (white) in a thin sheet of superconducting film. Green indicates strong superconductivity. Further away from the holes, the superconductivity decreases (yellow, red and finally black, where the material is densely populated with vortices that interfere with superconductivity. No image credit

    The team discovered a way to efficiently stabilize tiny magnetic vortices that interfere with superconductivity—a problem that has plagued scientists trying to engineer real-world applications for decades. The discovery could remove one of the most significant roadblocks to advances in superconductor technology.

    scwire
    This graphic shows a strip of superconducting wire with a chain of vortices (red). The green areas show strong superconductivity. Superimposed are two curves showing the resistance of the strip depending on the magnetic field; as the magnetic field increases, the resistance first grows, then drops dramatically. No image credit.

    See the full article here.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus


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