MSGID: 1:317/3 63e719f0   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Researchers detail never-before-seen properties in a family of   
   superconducting Kagome metals    
      
     Date:   
         February 10, 2023   
     Source:   
         Brown University   
     Summary:   
         Researchers have used an innovative new strategy combining nuclear   
         magnetic resonance imaging and a quantum modeling theory to describe   
         the microscopic structure of Kagome superconductor RbV3Sb5 at 103   
         degrees Kelvin, which is equivalent to about 275 degrees below 0   
         degrees Fahrenheit.   
      
      
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   FULL STORY   
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   Dramatic advances in quantum computing, smartphones that only need to be   
   charged once a month, trains that levitate and move at superfast speeds.   
      
   Technological leaps like these could revolutionize society, but they   
   remain largely out of reach as long as superconductivity -- the flow of   
   electricity without resistance or energy waste -- isn't fully understood.   
      
      
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   One of the major limitations for real-world applications of this   
   technology is that the materials that make superconducting possible   
   typically need to be at extremely cold temperatures to reach that level   
   of electrical efficiency. To get around this limit, researchers need to   
   build a clear picture of what different superconducting materials look   
   like at the atomic scale as they transition through different states of   
   matter to become superconductors.   
      
   Scholars in a Brown University lab, working with an international team   
   of scientists, have moved a small step closer to cracking this mystery   
   for a recently discovered family of superconducting Kagome metals. In   
   a new study, they used an innovative new strategy combining nuclear   
   magnetic resonance imaging and a quantum modeling theory to describe   
   the microscopic structure of this superconductor at 103 degrees Kelvin,   
   which is equivalent to about 275 degrees below 0 degrees Fahrenheit.   
      
   The researchers described the properties of this bizarre state of   
   matter for what's believed to be the first time in Physical Review   
   Research. Ultimately, the findings represent a new achievement   
   in a steady march toward superconductors that operate at higher   
   temperatures. Superconductors that can operate at room temperature (or   
   close to it) are considered the holy grail of condensed-matter physics   
   because of the tremendous technological opportunities they would open in   
   power efficiency, including in electricity transmission, transportation   
   and quantum computing.   
      
   "If you are ever going to engineer something and make it commercial,   
   you need to know how to control it," said Brown physics professor Vesna   
   Mitrovi?, who leads a condensed matter NMR group at the University and   
   is a co-author on the new study. "How do we describe it? How do we tweak   
   it so that we get what we want? Well, the first step in that is you   
   need to know what the states are microscopically. You need to start to   
   build a complete picture of it."  The new study focuses on superconductor   
   RbV3Sb5, which is made of the metals rubidium vanadium and antimony. The   
   material earns its namesake because of its peculiar atomic structure,   
   which resembles a basketweave pattern that features interconnected   
   star-shaped triangles. Kagome materials fascinate researchers because   
   of the insight they provide into quantum phenomena, bridging two of the   
   most fundamental fields of physics -- topological quantum physics and   
   condensed matter physics.   
      
   Previous work from different groups established that this material goes   
   through a cascade of different phase transitions when the temperature   
   is lowered, forming different states of matter with different exotic   
   properties. When this material is brought to 103 degrees Kelvin, the   
   structure of lattice changes and the material exhibits what's known   
   as a charge-density wave, where the electrical charge density jumps up   
   and down. Understanding these jumps is important for the development of   
   theories that describe the behavior of electrons in quantum materials   
   like superconductors.   
      
   What hadn't been seen before in this type of Kagome metal was what the   
   physical structure of this lattice and charge order looked like at the   
   temperature the researchers were looking at, which is highest temperature   
   state where the metal starts transitioning between different states   
   of matter.   
      
   Using a new strategy combining NMR measurements and a modeling theory   
   known as density functional theory that's used to simulate the electrical   
   structure and position of atoms, the team was able to describe the new   
   structure the lattice changes into and its charge-density wave.   
      
   They showed that the structure moves from a 2x2x1 pattern with a signature   
   Star of David pattern to a 2x2x2 pattern. This happens because the   
   Kagome lattice inverts in on itself when the temperature gets extremely   
   frigid. The new lattice it transitions into is made up largely of separate   
   hexagons and triangles, the researchers showed. They also showed how   
   this pattern connects when they take one plane of the RbV3Sb5 structure   
   and rotate it, ``gazing '' into it from a different angle.   
      
   "It's as if this one Kagome now becomes these complicated things that   
   split in two," Mitrovi? said. "It stretches the lattice so that the Kagome   
   becomes this combination of hexagons and triangles in one plane and then   
   in the next plane over, after you rotate it half a circle, it repeats   
   itself."  Probing this atomic structure is a necessary step to providing   
   a complete portrait of the exotic states of matter this superconducting   
   material transitions into, the researchers said. They believe the findings   
   will lead to further prodding on whether this formation and its properties   
   can help superconductivity or if it's something that should be suppressed   
   to make better superconductors. The new unique technique they used will   
   also allow the researchers to answer a whole new set of questions.   
      
   "We know what this is now and our next job is to figure out what is the   
   relationship to other bizarre phases at low temperature -- does it help,   
   does it compete, can we control it, can we make it happen at higher   
   temperatures, if it's useful?" Mitrovi? said. "Next, we keep lowering   
   the temperature and learning more."  The experimental research was   
   led by Jonathan Frassineti, a joint graduate student between Brown and   
   the University of Bologna, Pietro Bonfa` from the University of Parma,   
   and two Brown students: Erick Garcia and Rong Cong.   
      
   Theoretical work was led by Bonfa` while all the materials were   
   synthesized at the University of California Santa Barbara. This research   
   included funding from the National Science Foundation.   
      
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Physics # Quantum_Physics # Materials_Science #   
                   Inorganic_Chemistry   
             o Computers_&_Math   
                   # Quantum_Computers # Spintronics_Research #   
                   Computers_and_Internet # Information_Technology   
       * RELATED_TERMS   
             o Absolute_zero o Magnetic_resonance_imaging   
             o Bose-Einstein_condensate o Speed_of_sound o   
             Resonance_(chemistry) o Quantum_number o Supercomputer o   
             Linus_Pauling   
      
   ==========================================================================   
   Story Source: Materials provided by Brown_University. Note: Content may   
   be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Jonathan Frassineti, Pietro Bonfa`, Giuseppe Allodi, Erick Garcia,   
      Rong   
         Cong, Brenden R. Ortiz, Stephen D. Wilson, Roberto De Renzi,   
         Vesna F.   
      
         Mitrović, Samuele Sanna. Microscopic nature of the   
         charge-density wave in the kagome superconductor RbV3Sb5. Physical   
         Review Research, 2023; 5 (1) DOI: 10.1103/PhysRevResearch.5.L012017   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230210185152.htm   
      
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