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  • richardmitnick 1:44 pm on April 27, 2018 Permalink | Reply
    Tags: , , Majorana fermion science, , Physics Illinois, , Superconductivity, , Topological quantum computation,   

    From Physics Illinois: “Topological insulator �flips� for superconductivity” 

    U Illinois bloc

    Physics Illinois

    U Illinois Physics bloc

    4/27/2018
    Siv Schwink

    Topology meets superconductivity through innovative reverse-order sample preparation.

    1
    (L-R) Professor of Physics James Eckstein, his graduate student Yang Bai, and Professor of Physics Tai-Chang Chiang pose in front of the atomic layer by layer molecular beam epitaxy system used to grow the topological insulator thin-film samples for this study, in the Eckstein laboratory at the University of Illinois. Photo by L. Brian Stauffer, University of Illinois at Urbana-Champaign.

    A groundbreaking sample preparation technique has enabled researchers at the University of Illinois at Urbana-Champaign and the University of Tokyo to perform the most controlled and sensitive study to date of a topological insulator (TI) closely coupled to a superconductor (SC). The scientists observed the superconducting proximity effect—induced superconductivity in the TI due to its proximity to the SC—and measured its relationship to temperature and the thickness of the TI.

    TIs with induced superconductivity are of paramount interest to physicists because they have the potential to host exotic physical phenomena, including the elusive Majorana fermion—an elementary particle theorized to be its own antiparticle—and to exhibit supersymmetry—a phenomenon reaching beyond the standard model that would shed light on many outstanding problems in physics. Superconducting TIs also hold tremendous promise for technological applications, including topological quantum computation and spintronics.

    Naturally occurring topological superconductors are rare, and those that have been investigated have exhibited extremely small superconducting gaps and very low transition temperatures, limiting their usefulness for uncovering the interesting physical properties and behaviors that have been theorized.

    TIs have been used in engineering superconducting topological superconductors (TI/SC), by growing TIs on a superconducting substrate. Since their experimental discovery in 2007, TIs have intrigued condensed matter physicists, and a flurry of theoretical and experimental research taking place around the globe has explored the quantum-mechanical properties of this extraordinary class of materials. These 2D and 3D materials are insulating in their bulk, but conduct electricity on their edges or outer surfaces via special surface electronic states which are topologically protected, meaning they can’t be easily destroyed by impurities or imperfections in the material.

    But engineering such TI/SC systems via growing TI thin films on superconducting substrates has also proven challenging, given several obstacles, including lattice structure mismatch, chemical reactions and structural defects at the interface, and other as-yet poorly understood factors.

    2
    The �flip-chip� cleavage-based sample preparation: (A) A photo and a schematic diagram of assembled Bi2Se3(0001)/Nb sample structure before cleavage. (B) Same sample structure after cleavage exposing a �fresh� surface of the Bi2Se3 film with a pre-determined thickness. Image courtesy of James Eckstein and Tai-Chang-Chiang, U. of I. Department of Physics and Frederick Seitz Materials Research Laboratory.

    Now, a novel sample-growing technique developed at the U. of I. has overcome these obstacles. Developed by physics professor James Eckstein in collaboration with physics professor Tai-Chang Chiang, the new “flip-chip” TI/SC sample-growing technique allowed the scientists to produce layered thin-films of the well-studied TI bismuth selenide on top of the prototypical SC niobium—despite their incompatible crystalline lattice structures and the highly reactive nature of niobium.

    These two materials taken together are ideal for probing fundamental aspects of the TI/SC physics, according to Chiang: “This is arguably the simplest example of a TI/SC in terms of the electronic and chemical structures. And the SC we used has the highest transition temperature among all elements in the periodic table, which makes the physics more accessible. This is really ideal; it provides a simpler, more accessible basis for exploring the basics of topological superconductivity,” Chiang comments.

    The method allows for very precise control over sample thickness, and the scientists looked at a range of 3 to 10 TI layers, with 5 atomic layers per TI layer. The team’s measurements showed that the proximity effect induces superconductivity into both the bulk states and the topological surface states of the TI films. Chiang stresses, what they saw gives new insights into superconducting pairing of the spin-polarized topological surface states.

    “The results of this research are unambiguous. We see the signal clearly,” Chiang sums up. “We investigated the superconducting gap as a function of TI film thickness and also as a function of temperature. The results are pretty simple: the gap disappears as you go above niobium’s transition temperature. That’s good—it’s simple. It shows the physics works. More interesting is the dependence on the thickness of the film. Not surprisingly, we see the superconducting gap reduces for increasing TI film thickness, but the reduction is surprisingly slow. This observation raises an intriguing question regarding how the pairing at the film surface is induced by coupling at the interface.”

    Chiang credits Eckstein with developing the ingenious sample preparation method. It involves assembling the sample in reverse order, on top of a sacrificial substrate of aluminum oxide, commonly known as the mineral sapphire. The scientists are able to control the specific number of layers of TI crystals grown, each of quintuple atomic thickness. Then a polycrystalline superconducting layer of niobium is sputter-deposited on top of the TI film. The sample is then flipped over and the sacrificial layer that had served as the substrate is dislodged by striking a “cleavage pin.” The layers are cleaved precisely at the interface of the TI and aluminum oxide.

    3
    A close-up shot of the atomic layer by layer molecular beam epitaxy system used to grow the topological insulator thin-film samples for this study, located in the Eckstein laboratory at the University of Illinois. Photo by L. Brian Stauffer, University of Illinois at Urbana-Champaign.

    Eckstein explains, “The ‘flip-chip’ technique works because the layers aren’t strongly bonded—they are like a stack of paper, where there is strength in the stack, but you can pull apart the layers easily. Here, we have a triangular lattice of atoms, which comes in packages of five—these layers are strongly bonded. The next five layers sit on top, but are weakly bonded to the first five. It turns out, the weakest link is right at the substrate-TI interface. When cleaved, this method gives a pure surface, with no contamination from air exposure.”

    The cleavage was performed in an ultrahigh vacuum, within a highly sensitive instrument at the Institute for Solid State Physics at the University of Tokyo capable of angle-resolved photoemission spectroscopy (ARPES) at a range of temperatures.

    Chiang acknowledges, “The superconducting features occur at very small energy scales—it requires a very high energy resolution and very low temperatures. This portion of the experiment was completed by our colleagues in the University of Tokyo, where they have the instruments with the sensitivity to get the resolution we need for this kind of study. We couldn’t have done this without this international collaboration.”

    “This new sample preparation method opens up many new avenues in research, in terms of exotic physics, and, in the long term, in terms of possible useful applications—potentially even including building a better superconductor. It will allow preparation of samples using a wide range of other TIs and SCs. It could also be useful in miniaturization of electronic devices, and in spintronic computing, which would require less energy in terms of heat dissipation,” Chiang concludes.

    Eckstein adds, “There is a lot of excitement about this. If we can make a superconducting TI, theoretical predictions tell us that we could find a new elementary excitation that would make an ideal topological quantum bit, or qubit. We’re not there yet, and there are still many things to worry about. But it would be a qubit whose quantum mechanical wave function would be less susceptible to local perturbations that might cause dephasing, messing up calculations.”

    These findings were published online on 27 April 2018 in the journal Science Advances.

    See the full article here .

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  • richardmitnick 1:03 pm on April 9, 2018 Permalink | Reply
    Tags: , Physicists Just Discovered an Entirely New Type of Superconductivity, , , Superconductivity,   

    From University of Maryland via Science Alert: “Physicists Just Discovered an Entirely New Type of Superconductivity “ 

    U Maryland bloc

    University of Maryland

    Science Alert

    9 APR 2018
    FIONA MACDONALD

    “No one thought this was possible in solid materials.”

    1
    (Emily Edwards, University of Maryland)

    One of the ultimate goals of modern physics is to unlock the power of superconductivity, where electricity flows with zero resistance at room temperature.

    Progress has been slow, but physicists have just made an unexpected breakthrough. They’ve discovered a superconductor that works in a way no one’s ever seen before – and it opens the door to a whole world of possibilities not considered until now.

    In other words, they’ve identified a brand new type of superconductivity.

    Why does that matter? Well, when electricity normally flows through a material – for example, the way it travels through wires in the wall when we switch on a light – it’s fast, but surprisingly ineffective.

    Electricity is carried by electrons, which bump into atoms in the material along the way, losing some of their energy each time they have one of these collisions. Known as resistance, it’s the reason why electricity grids lose up to 7 percent of their electricity.

    But when some materials are chilled to ridiculously cold temperatures, something else happens – the electrons pair up, and begin to flow orderly without resistance.

    This is known as superconductivity, and it has incredible potential to revolutionise our world, making our electronics unimaginably more efficient.

    The good news is we’ve found the phenomenon in many materials so far. In fact, superconductivity is already used to create the strong magnetic fields in MRI machines and maglev trains.

    The bad news is that it currently requires expensive and bulky equipment to keep the superconductors cold enough to achieve this phenomenon – so it remains impractical for broader use.

    Now researchers led by the University of Maryland have observed a new type of superconductivity when probing an exotic material at super cool temperatures.

    Not only does this type of superconductivity appear in an unexpected material, the phenomenon actually seems to rely on electron interactions that are profoundly different from the pairings we’ve seen to date. And that means we have no idea what kind of potential it might have.

    To understand the difference, you need to know that the way electrons interact is dictated by a quantum property called spin.

    In regular superconductors, electrons carry a spin referred to as 1/2.

    But in this particular material, known as YPtBi, the team found that something else was going on – the electrons appear to have a spin of 3/2.

    “No one had really thought that this was possible in solid materials,” explains physicist and senior author Johnpierre Paglione.

    “High-spin states in individual atoms are possible but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half. ”

    YPtBi was first discovered to be a superconductor a couple of years ago, and that in itself was a surprise, because the material doesn’t actually fit one of the main criteria – being a relatively good conductor, with a lot of mobile electrons, at normal temperatures.

    According to conventional theory, YPtBi would need about a thousand times more mobile electrons in order to become superconducting at temperatures below 0.8 Kelvin.

    But when researchers cooled the material down, they saw superconductivity happening anyway.

    To figure out what was going on, the latest study looked at the way the material interacted with magnetic fields to get a sense of exactly what was going on inside.

    Usually as a material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its surface – but a magnetic field can still enter near, before quickly decaying away. How far they penetrate depends on the nature of the electron pairing happening within.

    The team used copper coils to detect changes in YPtBi’s magnetic properties as they changed its temperature.

    What they found was odd – as the material warmed up from absolute zero, the amount that a magnetic field could penetrate the material increased linearly instead of exponentially, which is what is normally seen with superconductors.

    After running a series of measurements and calculations, the researched concluded that the best explanation for what was going on was that the electrons must have been disguised as particles with higher spin – something that wasn’t even considered as a possibility for a superconductor before.

    While this new type of superconductivity still requires incredibly cold temperatures for now, the discovery gives the entire field a whole new direction.

    “We used to be confined to pairing with spin one-half particles,” says lead author Hyunsoo Kim.

    “But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting.”

    This is incredibly early days, and there’s still a lot we have to learn about exactly what’s going on here.

    But the fact that we have a brand new type of superconductivity to test and measure, adding a cool new breakthrough to the 100 years of this type of research, is pretty exciting.

    “When you have this high-spin pairing, what’s the glue that holds these pairs together?” says Paglione.

    “There are some ideas of what might be happening, but fundamental questions remain-which makes it even more fascinating.”

    The research has been published in Science Advances.

    See the full article here .

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    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 9:39 am on February 16, 2018 Permalink | Reply
    Tags: , , , , Superconductivity   

    From BNL: “Bringing a Hidden Superconducting State to Light” 

    Brookhaven Lab

    February 16, 2018
    Ariana Tantillo,
    atantillo@bnl.gov
    (631) 344-2347

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

    High-power light reveals the existence of superconductivity associated with charge “stripes” in the copper-oxygen planes of a layered material above the temperature at which it begins to transmit electricity without resistance.

    1
    Physicist Genda Gu holds a single-crystal rod of LBCO—a compound made of lanthanum, barium, copper, and oxygen—in Brookhaven’s state-of-the-art crystal growth lab. The infrared image furnace he used to synthesize these high-quality crystals is pictured in the background. No image credit.

    A team of scientists has detected a hidden state of electronic order in a layered material containing lanthanum, barium, copper, and oxygen (LBCO). When cooled to a certain temperature and with certain concentrations of barium, LBCO is known to conduct electricity without resistance, but now there is evidence that a superconducting state actually occurs above this temperature too. It was just a matter of using the right tool—in this case, high-intensity pulses of infrared light—to be able to see it.

    Reported in a paper published in the Feb. 2 issue of Science, the team’s finding provides further insight into the decades-long mystery of superconductivity in LBCO and similar compounds containing copper and oxygen layers sandwiched between other elements. These “cuprates” become superconducting at relatively higher temperatures than traditional superconductors, which must be frozen to near absolute zero (minus 459 degrees Fahrenheit) before their electrons can flow through them at 100-percent efficiency. Understanding why cuprates behave the way they do could help scientists design better high-temperature superconductors, eliminating the cost of expensive cooling systems and improving the efficiency of power generation, transmission, and distribution. Imagine computers that never heat up and power grids that never lose energy.

    “The ultimate goal is to achieve superconductivity at room temperature,” said John Tranquada, a physicist and leader of the Neutron Scatter Group in the Condensed Matter Physics and Materials Science Department at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, where he has been studying cuprates since the 1980s. “If we want to do that by design, we have to figure out which features are essential for superconductivity. Teasing out those features in such complicated materials as the cuprates is no easy task.”

    The copper-oxygen planes of LBCO contain “stripes” of electrical charge separated by a type of magnetism in which the electron spins alternate in opposite directions. In order for LBCO to become superconducting, the individual electrons in these stripes need to be able to pair up and move in unison throughout the material.

    Previous experiments showed that, above the temperature at which LBCO becomes superconducting, resistance occurs when the electrical transport is perpendicular to the planes but is zero when the transport is parallel. Theorists proposed that this phenomenon might be the consequence of an unusual spatial modulation of the superconductivity, with the amplitude of the superconducting state oscillating from positive to negative on moving from one charge stripe to the next. The stripe pattern rotates by 90 degrees from layer to layer, and they thought that this relative orientation was blocking the superconducting electron pairs from moving coherently between the layers.

    “This idea is similar to passing light through a pair of optical polarizers, such as the lenses of certain sunglasses,” said Tranquada. “When the polarizers have the same orientation, they pass light, but when their relative orientation is rotated to 90 degrees, they block all light.”

    However, a direct experimental test of this picture had been lacking—until now.

    One of the challenges is synthesizing the large, high-quality single crystals of LBCO needed to conduct experiments. “It takes two months to grow one crystal, and the process requires precise control over temperature, atmosphere, chemical composition, and other conditions,” said co-author Genda Gu, a physicist in Tranquada’s group. Gu used an infrared image furnace—a machine with two bright lamps that focus infrared light onto a cylindrical rod containing the starting material, heating it to nearly 2500 degrees Fahrenheit and causing it to melt—in his crystal growth lab to grow the LBCO crystals.

    Collaborators at the Max Planck Institute for the Structure and Dynamics of Matter and the University of Oxford then directed infrared light, generated from high-intensity laser pulses, at the crystals (with the light polarization in a direction perpendicular to the planes) and measured the intensity of light reflected back from the sample. Besides the usual response—the crystals reflected the same frequency of light that was sent in—the scientists detected a signal three times higher than the frequency of that incident light.

    “For samples with three-dimensional superconductivity, the superconducting signature can be seen at both the fundamental frequency and at the third harmonic,” said Tranquada. “For a sample in which charge stripes block the superconducting current between layers, there is no optical signature at the fundamental frequency. However, by driving the system out of equilibrium with the intense infrared light, the scientists induced a net coupling between the layers, and the superconducting signature shows up in the third harmonic. We had suspected that the electron pairing was present—it just required a stronger tool to bring this superconductivity to light.”

    University of Hamburg theorists supported this experimental observation with analysis and numerical simulations of the reflectivity.

    This research provides a new technique to probe different types of electronic orders in high-temperature superconductors, and the new understanding may be helpful in explaining other strange behaviors in the cuprates.

    The work performed at Brookhaven was supported by DOE’s Office of Science.

    See the full article here .

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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 7:35 am on July 7, 2017 Permalink | Reply
    Tags: , , , , , Superconductivity   

    From BNL: “Electron Orbitals May Hold Key to Unifying Concept of High-Temperature Superconductivity” 

    Brookhaven Lab

    July 6, 2017
    Karen McNulty Walsh,
    kmcnulty@bnl.gov
    (631) 344-8350

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

    1
    Iron-based superconductivity occurs in materials such as iron selenide (FeSe) that contain crystal planes made up of a square array of iron (Fe) atoms, depicted here. In these iron layers, each Fe atom has two active electron “clouds,” or orbitals—dxz (red) and dyz (blue)—each containing one electron. By directly visualizing the electron states in the iron planes of FeSe, the researchers revealed that that electrons in the dxz orbitals (red) do not form Cooper pairs or contribute to the superconductivity, but instead form an incoherent metallic state along the horizontal (x) axis. In contrast, all electrons in the dyz orbitals (blue) form strong Cooper pairs with neighboring atoms to generate superconductivity. Searching for other materials with this exotic “orbital-selective” pairing may lead to the discovery of new superconductors. No image credit.

    2
    The custom-built Spectroscopic Imaging Scanning Tunneling Microscope used for these experiments stands one meter high, with cryogenic circuitry at the top for cooling samples to temperatures just above absolute zero (nearly -273 degrees Celsius). Inside, a needle with single atom on the end scans across the crystal surface in steps as small as 2 trillionths of a meter, measuring the electron tunneling current at each location. These measurements reveal the quantum wavefunctions of electrons in the material with exquisite precision. No image credit.

    A team of scientists has found evidence for a new type of electron pairing that may broaden the search for new high-temperature superconductors. The findings, described in the journal Science, provide the basis for a unifying description of how radically different “parent” materials—insulating copper-based compounds and metallic iron-based compounds—can develop the ability to carry electrical current with no resistance at strikingly high temperatures.

    According to the scientists, the materials’ dissimilar electronic characteristics actually hold the key to commonality.

    See the full article here .

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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 11:23 am on July 3, 2017 Permalink | Reply
    Tags: , Center for Emergent Superconductivity, Chemical doping, , Electrolyte gating, , Superconductivity   

    From BNL: “Brookhaven Scientists Study Role of ‘Electrolyte Gating’ in Functional Oxide Materials” 

    Brookhaven Lab

    July 3, 2017
    Stephanie Kossman
    skossman@bnl.gov
    (631) 344-8671

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

    1
    No image caption or credit.

    Physicists at the U.S. Department of Energy’s Brookhaven National Laboratory have broken new ground in the study of functional oxide materials. The researchers discovered a previously unknown mechanism involved in “electrolyte gating,” a method for increasing electrical conductivity in materials and potentially inducing superconductivity. Their work was published on Monday, July 3 in Quantum Materials, a Nature partner journal.

    Superconductivity is the ability of a material to conduct electricity with zero loss or resistance. This effect is 100 percent efficient but has only been achieved at extremely cold temperatures, making it impractical for most large-scale applications. In Brookhaven’s Oxide Molecular Beam Epitaxy Group, led by Ivan Bozovic, researchers have been investigating oxides – chemical compounds with oxygen atoms – as potential high-temperature superconductors.

    Seeking to induce superconductivity in tungsten oxide, the researchers used a method called electrolyte gating. In this technique, electrically charged compounds draw ions with opposite charges away from each other, creating large electric fields and increasing a material’s electrical conductivity.

    Similar effects have traditionally been produced using a technique called chemical doping, which requires scientists to add new atoms to materials. Though productive, chemical doping is inefficient for finding new materials with interesting and useful properties because the conductivity of “doped” materials is fixed and cannot be easily changed if researchers want to test a material under different conditions.

    On the other hand, “Electrolyte gating allows you to tune materials,” said Tony Bollinger, a physicist at Brookhaven and one of the paper’s authors. “You can have one sample that you grow and then can continuously change—or tune—as you test it. It saves you from having to go back and synthesize new materials.”

    Until now, the underlying mechanisms of electrolyte gating were not fully understood. There were two competing theories, one focused on an electrostatic effect, another focused on an oxygen-related (electrochemical) effect. The team at Brookhaven, however, discovered an entirely new mechanism at play, where hydrogen plays a key role.

    By using a new method for patterning materials, the researchers were able to monitor the electrical resistance in sections near the site of electrolyte gating, not just in the immediate area. In this area, they observed a drop in resistance and a migration of positive charge. Based on the distance the charge moved, they were able to determine hydrogen atoms were moving through tungsten oxide.

    “This means there is no universal mechanism for electrolyte gating,” Bollinger said. “It’s not always purely electrostatic or electrochemical. You have to look at your specific material and see what is going on there. Our findings give us a guide as we move forward and apply electrolyte gating to other materials.”

    Brookhaven’s researchers also developed other new techniques to confirm their observations in this study. For example, they grew materials with different layers of thickness in order to measure electrical resistance in progressively thicker portions of the material, finding electrolyte gating was affecting the whole material, not just the surface.

    “These techniques will increase the number of ways we can probe materials to see exactly what the influence of electrolyte gating is on them,” Bollinger said.

    Moving forward, the researchers say electrolyte gating can be used as a more efficient alternative to chemical doping and could speed up the process of discovering new superconducting materials.

    This work was supported in part by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by DOE’s Office of Science.

    See the full article here .

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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 9:08 am on May 10, 2017 Permalink | Reply
    Tags: A laser-guided path to diamond superconductors?, , , , Raman spectroscopy, Superconductivity   

    From COSMOS: “A laser-guided path to diamond superconductors?” 

    Cosmos Magazine bloc

    COSMOS

    10 May 2017
    Andrew Stapleton

    1
    A diamond, recently. Mina De La O / Getty

    Besides glittering beautifully in the sun, diamonds have another attractive property: they can become superconductive. Superconductivity occurs when a material has zero electrical resistance and is normally only seen when the material is chilled to temperatures very close to absolute zero (around –273 °C), which severely limits the use of superconductors in commercial applications.

    Scientists from India and Israel conducted the first systematic study to understand how doping diamond with boron effects its ability to become superconducting. They reported their findings in Applied Physics Letters.

    The scientists fabricated a series of thin diamond films doped with increasing levels of boron and monitored the samples with a technique called Raman spectroscopy. This technique uses pulses of laser light at specific wavelengths to measure the unique energy states in materials. Raman spectroscopy can be used for analysing the makeup of material or, as in this study, to watch how the energy states are affected by impurities.

    Associate Professor Rongkun Zheng of the University of Sydney, a physicist not involved with the study, said: “Raman scattering probes the vibration and rotation of atoms or molecules in a sample, which is related to the superconductivity of the material.”

    The team noticed a remarkable change in the energy states of the doped diamond. They concluded that their study provided a new understanding of how impurities effect the energy levels in diamonds and, perhaps more tenuously, that this could lead to a superconductive material that doesn’t have to be chilled to absolute zero.

    The results, they believe, could inform the fabrication of materials for future applications such as high-performance electrical grids and high-speed transport.

    Zheng, however, is less convinced. “The paper emphasised superconductivity but did not explore the effect on superconductivity. The significance and quality of this paper is very limited.”

    See the full article here .

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  • richardmitnick 2:44 pm on March 4, 2017 Permalink | Reply
    Tags: , , , Superconductivity   

    From COSMOS: “Resistance is futile: the super science of superconductivity” 

    Cosmos Magazine bloc

    COSMOS

    30 May 2016 [Re-issued?]
    Cathal O’Connell

    From maglev trains to prototype hoverboards and the Large Hadron Collider – superconductors are finding more and more uses for modern technology. What superconductors are and how they work.

    1
    A superconducting ceramic operates at the relatively high temperature of 123 Kelvin in a Japanese lab.
    TAKESHI TAKAHARA

    What are superconductors?

    All the electronic devices around you – your phone, your computer, even your bedside lamp – are based on moving electrons through materials. In most materials, there is an opposition to this movement (kind of like friction, but for electrons) called electrical resistance, which wastes some of the energy as heat.

    This is why your laptop heats up during use, and the same effect is used to boil water in a kettle.

    Superconductors are materials that carry electrical current with exactly zero electrical resistance. This means you can move electrons through it without losing any energy to heat.

    Sounds amazing. What’s the catch?

    The snag is you have to cool a superconductor below a critical temperature for it to work. That critical temperature depends on the material, but it’s usually below -100 °C.

    A room temperature superconductor, if one could be found, could revolutionise modern technology, letting us transmit power across continents without any loss.

    How was superconductivity discovered?

    When you cool a metal, its electrical resistance tends to decrease. This is because the atoms in the metal jiggle around less, and so are less likely to get in an electrons way.

    Around the turn of the 19th century, physicists were debating what would happen at absolute zero, when the jiggling stops altogether.

    Some wondered whether the resistance would continue to decrease until it reached zero.

    Others, such as Lord Kelvin (after whom the temperature scale is named), argued that the resistance would become infinite as electrons themselves would stop moving.

    In April 1911, Dutch physicist Heike Kamerlingh Onnes cooled a solid mercury wire to 4.2 Kelvin and found the electrical resistance suddenly vanished – the mercury became a perfect conductor. It was a shocking discovery, both because of the abruptness of the change, and the fact it happened still a good four degrees above absolute zero.

    Kamerlingh Onnes had discovered superconductivity, although it took another 40 years for his results to be fully explained.

    What’s the explanation for superconductivity?

    It turns out there are at least two kinds of superconductivity, and physicists can only explain one of them.

    In the simplest case, when you cool a single element down below its critical temperature (as with the mercury example above) physicists can explain superconductivity pretty well: it arises from a weird quantum effect which causes the electrons to pair up within the material. When paired, the electrons gain the ability to flow through the material without getting knocked about by atoms.

    But more complex materials, such as some ceramics which are superconducting at higher temperatures, can’t be explained using this theory.

    Physicists don’t have a good explanation for what causes superconductivity in these “non-traditional superconductor” materials, although the answer must be another quantum effect which links up the electrons in some way.

    What are high-temperature superconductors?

    Physicists have a loose definition of what a “high temperature” is. In this case, it usually means anything above 70 Kelvin (or -203 °C). They choose this temperature because it means the superconductor can be cooled using liquid nitrogen, making it relatively cheap to run (liquid nitrogen only costs about 10-15 cents a litre.)

    The threshold temperature for superconductivity has been increasing for decades. The current record (-70 °C) is held by hydrogen sulfide (yes, the same molecule that gives rotten eggs their distinctive smell).

    The hope is that one day scientists will produce a material that superconducts at room temperature with no cooling required.

    What are superconductors used for now?

    Superconductors are used to make incredibly strong magnets for magnetic levitation (maglev) trains, for the magnetic resonance imaging (MRI) machines in hospitals, and to keep particles on track as they race around the Large Hadron Collider.

    CERN LHC particles
    CERN LHC particles

    The reason superconductors can make strong magnets comes down to Faraday’s law (a moving electric field creates a magnetic field). With no resistance, you can create a huge current, which makes for a correspondingly large magnetic field.

    For example, maglev trains have a series of superconducting coils along each wagon. Each superconductor contains a permanent electric current of about 700,000 amperes.

    2
    The Japanese SCMaglev’s EDS suspension is powered by the magnetic fields induced either side of the vehicle by the passage of the vehicle’s superconducting magnets.

    3
    http://science.howstuffworks.com/transport/engines-equipment/maglev-train.htm

    The current runs round and round the coil without ever winding down, and so the magnetic field it generates is constant and incredibly strong. As the train passes over other electromagnets in the track, it levitates.

    With no friction to slow them down, maglev trains can reach over 600 kilometres per hour, making them the fastest in the world.

    A prototype hoverboard designed by Lexus also uses superconducting magnets for levitation

    5
    Lexus via Wired

    What uses might superconductors have in the future?

    About 6% of all the electricity generated by power plants is lost in transmitting and distributing it around the country along copper wires.

    By replacing copper wires with superconducting wires, we could potentially transmit electrical power across entire continents without any loss. The problem, at the moment, is this would be ludicrously expensive.

    In 2014, the German city of Essen installed a kilometre-long superconducting cable for transmitting electrical power. It can transmit five times more power than a conventional cable, and with hardly any loss, although it’s a complicated bit of kit.

    To keep the superconductor below its critical temperature, liquid nitrogen must be pumped through the core and the whole thing is encased in several layers of insulation, a bit like a thermos flask.

    For a more practical solution, we’ll need to wait for cheap superconductors that can operate closer to room temperature, an advance that can be expected to take decades.

    Closer to reality, perhaps, are superconducting computers. Scientists have already developed computer chips based on superconductors, such as the Hypres Superconducting Microchip. Using such processors could lead to supercomputers requiring 1/50Oth the power of a regular supercomputer.

    6
    Hypres Superconducting Microchip, Incorporating 6000 Josephson Junctions. Noimage credit. http://www.superconductors.org/uses.htm

    See the full article here .

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  • richardmitnick 3:28 pm on December 23, 2016 Permalink | Reply
    Tags: , , Laser Pulses Help Scientists Tease Apart Complex Electron Interactions, Superconductivity   

    From BNL: “Laser Pulses Help Scientists Tease Apart Complex Electron Interactions” 

    Brookhaven Lab

    December 20, 2016
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350

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

    1
    A microscopic image of one of the bismuth strontium calcium copper oxide samples the scientists studied using a new high-speed imaging technique. Color changes show changes in sample height and curvature to dramatically reveal the layered structure and flatness of the material. No image credit.

    Scientists studying high temperature superconductors—materials that carry electric current with no energy loss when cooled below a certain temperature—have been searching for ways to study in detail the electron interactions thought to drive this promising property. One big challenge is disentangling the many different types of interactions—for example, separating the effects of electrons interacting with one another from those caused by their interactions with the atoms of the material.

    Now a group of scientists including physicists at the U.S. Department of Energy’s Brookhaven National Laboratory has demonstrated a new laser-driven “stop-action” technique for studying complex electron interactions under dynamic conditions. As described in a paper just published in Nature Communications, they use one very fast, intense “pump” laser to give electrons a blast of energy, and a second “probe” laser to measure the electrons’ energy level and direction of movement as they relax back to their normal state.

    “By varying the time between the ‘pump’ and ‘probe’ laser pulses we can build up a stroboscopic record of what happens—a movie of what this material looks like from rest through the violent interaction to how it settles back down,” said Brookhaven physicist Jonathan Rameau, one of the lead authors on the paper. “It’s like dropping a bowling ball in a bucket of water to cause a big disruption, and then taking pictures at various times afterward,” he explained.

    2
    Brookhaven Lab physicists Peter Johnson (rear) and Jonathan Rameau. No image credit.

    The technique, known as time-resolved, angle-resolved photoelectron spectroscopy (tr-ARPES), combined with complex theoretical simulations and analysis, allowed the team to tease out the sequence and energy “signatures” of different types of electron interactions. They were able to pick out distinct signals of interactions among excited electrons (which happen quickly but don’t dissipate much energy), as well as later-stage random interactions between electrons and the atoms that make up the crystal lattice (which generate friction and lead to gradual energy loss in the form of heat).

    But they also discovered another, unexpected signal—which they say represents a distinct form of extremely efficient energy loss at a particular energy level and timescale between the other two.

    “We see a very strong and peculiar interaction between the excited electrons and the lattice where the electrons are losing most of their energy very rapidly in a coherent, non-random way,” Rameau said. At this special energy level, he explained, the electrons appear to be interacting with lattice atoms all vibrating at a particular frequency—like a tuning fork emitting a single note. When all of the electrons that have the energy required for this unique interaction have given up most of their energy, they start to cool down more slowly by hitting atoms more randomly without striking the “resonant” frequency, he said.

    The frequency of the special lattice interaction “note” is particularly noteworthy, the scientists say, because its energy level corresponds with a “kink” in the energy signature of the same material in its superconducting state, which was first identified by Brookhaven scientists using a static form of ARPES. Following that discovery, many scientists suggested that the kink might have something to do with the material’s ability to become a superconductor, because it is not readily observed above the superconducting temperature.

    But the new time-resolved experiments, which were done on the material well above its superconducting temperature, were able to tease out the subtle signal. These new findings indicate that this special condition exists even when the material is not a superconductor.

    “We know now that this interaction doesn’t just switch on when the material becomes a superconductor; it’s actually always there,” Rameau said.

    The scientists still believe there is something special about the energy level of the unique tuning-fork-like interaction. Other intriguing phenomena have been observed at this same energy level, which Rameau says has been studied in excruciating detail.

    It’s possible, he says, that the one-note lattice interaction plays a role in superconductivity, but requires some still-to-be-determined additional factor to turn the superconductivity on.

    “There is clearly something special about this one note,” Rameau said.

    3
    Members of the research team: Peter Johnson and Jonathan Rameau of Brookhaven Lab with Laurenz Rettig, Manuel Ligges, and Isabella Avigo and their time-resolved ARPES experimental setup at the University Duisburg-Essen, Germany.

    Work at Brookhaven National Laboratory was supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center headquartered at Brookhaven National Laboratory and funded by the DOE Office of Science. Additional funding was provided by the National Science Foundation, the Aspen Center for Physics, the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory, and by the McDevitt bequest at

    Georgetown University. Computational resources were provided by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility headquartered at Lawrence Berkeley National Laboratory. Additional support came from Deutsche Forschungsgemeinschaft, the Mercator Research Center Ruhr, and from the European Union within the seventh Framework Program.

    See the full article here .

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    BNL Campus

    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 6:53 am on November 26, 2016 Permalink | Reply
    Tags: A distinct state of matter, , , , New Clues Emerge in 30-Year-Old Superconductor Mystery, Nonlinear optical rotational anisotropy, Pseudogap, Superconductivity   

    From Caltech: “New Clues Emerge in 30-Year-Old Superconductor Mystery” 

    Caltech Logo

    Caltech

    11/21/2016

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    An artistic representation of the data showing the breaking of spatial inversion and rotational symmetries in the pseudogap region of superconducting materials—evidence that the pseudogap is a distinct phase of matter. Rings of light reflected from a superconductor reveal the broken symmetries. Credit: Hsieh Lab/Caltech

    One of the greatest mysteries of experimental physics is how so-called high-temperature superconducting materials work. Despite their name, high-temperature superconductors—materials that carry electrical current with no resistance—operate at chilly temperatures less than minus 135 degrees Celsius. They can be used to make superefficient power cables, medical MRIs, particle accelerators, and other devices. Cracking the mystery of how these materials work could lead to superconducting devices that operate at room temperatures—and could revolutionize electrical devices, including laptops and phones.

    In a new paper in the journal Nature Physics, researchers with the Institute for Quantum Information and Matter at Caltech have at last solved one piece of this enduring puzzle. They have confirmed that a transitional phase of matter called the pseudogap—one that occurs before these materials are cooled down to become superconducting—represents a distinct state of matter, with properties very different from those of the superconducting state itself.

    When matter transitions from one state, or phase, to another—say, water freezing into ice—there is a change in the ordering pattern of the materials’ particles. Physicists previously had detected hints of some type of ordering of electrons inside the pseudogap state. But exactly how they were ordering—and whether that ordering constituted a new state of matter—was unclear until now.

    “A peculiar property of all these high-temperature superconductors is that just before they enter the superconducting state, they invariably first enter the pseudogap state, whose origins are equally if not more mysterious than the superconducting state itself,” says David Hsieh, professor of physics at Caltech and principal investigator of the new research. “We have discovered that in the pseudogap state, electrons form a highly unusual pattern that breaks nearly all of the symmetries of space. This provides a very compelling clue to the actual origin of the pseudogap state and could lead to a new understanding of how high-temperature superconductors work.”

    The phenomenon of superconductivity was first discovered in 1911. When certain materials are chilled to super-cold temperatures, as low as a few degrees above absolute zero (a few degrees Kelvin), they carry electrical current with no resistance, so that no heat or energy is lost. In contrast, our laptops are not made of superconducting materials and therefore experience electrical resistance and heat up.

    Chilling materials to such extremely low temperatures requires liquid helium. However, because liquid helium is rare and expensive, physicists have been searching for materials that can function as superconductors at ever-higher temperatures. The so-called high-temperature superconductors, discovered in 1986, are now known to operate at temperatures up to 138 Kelvin (minus 135 degrees Celsius) and thus can be cooled with liquid nitrogen, which is more affordable than liquid helium. The question that has eluded physicists, however—despite three Nobel Prizes to date awarded in the field of superconductivity—is exactly how high-temperatures superconductors work.

    The dance of superconducting electrons

    Materials become superconducting when electrons overcome their natural repulsion and form pairs. This pairing can occur under extremely cold temperatures, allowing the electrons, and the electrical currents they carry, to move unencumbered. In conventional superconductors, electron pairing is caused by natural vibrations in the crystal lattice of the superconducting material, which act like glue to hold the pairs together.

    But in high-temperature superconductors, this form of “glue” is not strong enough to bind the electron pairs. Researchers think that the pseudogap, and how electrons order themselves in this phase, holds clues about what this glue may constitute for high-temperature superconductors. To study electron ordering in the pseudogap, Hsieh and his team have invented a new laser-based method called nonlinear optical rotational anisotropy. In the method, a laser is pointed at the superconducting material; in this case, crystals of ytttrium barium copper oxide (YBa2Cu3Oy). An analysis of the light reflected back at half the wavelength compared to that going in reveals any symmetry in the arrangement of the electrons in the crystals.

    Broken symmetries point to new phase

    Different phases of matter have distinct symmetries. For example, when water turns into ice, physicists say the symmetry has been “broken.”

    “In water,” Hsieh explains, “the H2O molecules are pretty randomly oriented. If you were swimming in an infinite pool of water, your surroundings look the same no matter where you are. In ice, on the other hand, the H2O molecules form a regular periodic network, so if you imagine yourself submerged in an infinite block of ice, your surroundings appear different depending on whether you are sitting on an H or O atom. Therefore, we say that the translational symmetry of space is broken in going from water to ice.”

    With the new tool, Hsieh’s team was able to show that the electrons cooled to the pseudogap phase broke a specific set of spatial symmetries called inversion and rotational symmetry. “As soon as the system entered the pseudogap region, either as a function of temperature or the amount of oxygen in the compound, there was a loss of inversion and rotational symmetries, clearly indicating a transition into a new phase of matter,” says Liuyan Zhao, a postdoctoral scholar in the Hsieh lab and lead author of the new study. “It is exciting that we are using a new technology to solve an old problem.”

    “The discovery of broken inversion and rotational symmetries in the pseudogap drastically narrows down the set of possibilities for how the electrons are self-organizing in this phase,” says Hsieh. “In some ways, this unusual phase may turn out to be the most interesting aspect of these superconducting materials.”

    The Nature Physics study, entitled A global-inversion-symmetry-broken phase inside the pseudogap region of YBa2Cu3Oy, was funded by the Army Research Office, the National Science Foundation, the Gordon and Betty Moore Foundation, the Canadian Institute for Advanced Research, and the Natural Sciences and Engineering Research Council. Other authors are C. A. Belvin of Wellesley College, Massachusetts; R. Liang, D.A. Bonn, and W.N. Hardy of the University of British Columbia, Vancouver; and N.P. Armitage of The Johns Hopkins University, Baltimore.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 10:19 am on October 17, 2016 Permalink | Reply
    Tags: , , , , , Superconductivity   

    From John A Paulson School of Engineering and Applied Sciences: “A new spin on superconductivity” 

    Harvard School of Engineering and Applied Sciences
    John A Paulson School of Engineering and Applied Sciences

    October 14, 2016
    Leah Burrows

    1

    Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have made a discovery that could lay the foundation for quantum superconducting devices. Their breakthrough solves one the main challenges to quantum computing: how to transmit spin information through superconducting materials.

    Every electronic device — from a supercomputer to a dishwasher — works by controlling the flow of charged electrons. But electrons can carry so much more information than just charge; electrons also spin, like a gyroscope on axis.

    Harnessing electron spin is really exciting for quantum information processing because not only can an electron spin up or down — one or zero — but it can also spin any direction between the two poles. Because it follows the rules of quantum mechanics, an electron can occupy all of those positions at once. Imagine the power of a computer that could calculate all of those positions simultaneously.

    A whole field of applied physics, called spintronics, focuses on how to harness and measure electron spin and build spin equivalents of electronic gates and circuits.

    By using superconducting materials through which electrons can move without any loss of energy, physicists hope to build quantum devices that would require significantly less power.

    But there’s a problem.

    According to a fundamental property of superconductivity, superconductors can’t transmit spin. Any electron pairs that pass through a superconductor will have the combined spin of zero.

    In work published recently in Nature Physics, the Harvard researchers found a way to transmit spin information through superconducting materials.

    “We now have a way to control the spin of the transmitted electrons in simple superconducting devices,” said Amir Yacoby, Professor of Physics and of Applied Physics at SEAS and senior author of the paper.

    It’s easy to think of superconductors as particle super highways but a better analogy would be a super carpool lane as only paired electrons can move through a superconductor without resistance.

    These pairs are called Cooper Pairs and they interact in a very particular way. If the way they move in relation to each other (physicists call this momentum) is symmetric, then the pair’s spin has to be asymmetric — for example, one negative and one positive for a combined spin of zero. When they travel through a conventional superconductor, Cooper Pairs’ momentum has to be zero and their orbit perfectly symmetrical.

    But if you can change the momentum to asymmetric — leaning toward one direction — then the spin can be symmetric. To do that, you need the help of some exotic (aka weird) physics.

    Superconducting materials can imbue non-superconducting materials with their conductive powers simply by being in close proximity. Using this principle, the researchers built a superconducting sandwich, with superconductors on the outside and mercury telluride in the middle. The atoms in mercury telluride are so heavy and the electrons move so quickly, that the rules of relativity start to apply.

    “Because the atoms are so heavy, you have electrons that occupy high-speed orbits,” said Hechen Ren, coauthor of the study and graduate student at SEAS. “When an electron is moving this fast, its electric field turns into a magnetic field which then couples with the spin of the electron. This magnetic field acts on the spin and gives one spin a higher energy than another.”

    So, when the Cooper Pairs hit this material, their spin begins to rotate.

    “The Cooper Pairs jump into the mercury telluride and they see this strong spin orbit effect and start to couple differently,” said Ren. “The homogenous breed of zero momentum and zero combined spin is still there but now there is also a breed of pairs that gains momentum, breaking the symmetry of the orbit. The most important part of that is that the spin is now free to be something other than zero.”

    The team could measure the spin at various points as the electron waves moved through the material. By using an external magnet, the researchers could tune the total spin of the pairs.

    “This discovery opens up new possibilities for storing quantum information. Using the underlying physics behind this discovery provides also new possibilities for exploring the underlying nature of superconductivity in novel quantum materials,” said Yacoby.

    This research was coauthored by Sean Hart, Michael Kosowsky, Gilad Ben-Shach, Philipp Leubner, Christoph Brüne, Hartmut Buhmann, Laurens W. Molenkamp and Bertrand I. Halperin.

    See the full article here .

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    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
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