Researchers describe never-before-seen properties in a family of superconducting Kagome metals – Zoo House News
- February 11, 2023
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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 super-fast speeds. Technological leaps like these could revolutionize society, but they remain largely elusive until superconductivity—the flow of electricity without resistance or wasted energy—is fully understood.
One of the major limitations for real-world applications of this technology is that the materials that enable superconductivity typically have to be exposed to extremely low temperatures to achieve this level of electrical efficiency. To get around this limit, researchers need to get a clear picture of what different superconducting materials look like at the atomic level as they go through different states of matter to become superconductors.
Scholars at a Brown University lab, in collaboration with an international team of scientists, have taken a small step closer to solving this mystery for a recently discovered family of superconducting kagome metals. In a new study, they used an innovative new strategy that combined magnetic resonance imaging and a quantum modeling theory to describe the microscopic structure of this superconductor at 103 degrees Kelvin, which is about 275 degrees below 0 degrees Fahrenheit.
The researchers probably first described the properties of this bizarre state of matter in Physical Review Research. Ultimately, the results represent a new achievement on the steady road to superconductors that operate at higher temperatures. Superconductors that can operate at (or close to) room temperature are considered the holy grail of condensed matter physics, including power transmission, transportation, and quantum computing, due to the tremendous technological possibilities they would open up in energy efficiency.
“If you ever want to engineer something and make it commercial, you need to know how to control it,” said Brown physics professor Vesna Mitrović, who leads a condensed matter NMR group at the university and is a co-author of the new study. “How do we describe it? How do we optimize it to get what we want? Well, the first step to this is that you need to know how the conditions are microscopic. You need to start getting a full picture of it. “
The new study focuses on the superconductor RbV3Sb5, which consists of the metals rubidium vanadium and antimony. The material earns its namesake because of its particular atomic structure, resembling a basket weave made up of interconnected star-shaped triangles. Kagome materials are fascinating researchers because of the insight they offer into quantum phenomena, bridging two of the most fundamental areas of physics – topological quantum physics and condensed matter physics.
Previous work by different groups has shown that this material undergoes a cascade of different phase transitions as the temperature is lowered, giving rise to different states of matter with different exotic properties. When this material is brought to 103 degrees Kelvin, the lattice structure changes and the material shows what is known as a charge density wave, in which the electrical charge density jumps up and down. Understanding these jumps is important for developing theories that describe the behavior of electrons in quantum materials such as superconductors.
What hasn’t been seen before with this type of kagome metal is what the physical structure of this lattice and charge order looked like at the temperature the researchers were looking at, the highest temperature state at which the metal begins to transition between different states of matter.
Using a new strategy that combines NMR measurements and a modeling theory known as density functional theory, which is used to simulate the electrical structure and position of atoms, the team was able to identify the new structure to which the lattice changes and its to describe the charge density wave.
They showed that the structure moves from a 2x2x1 pattern with a characteristic Star of David pattern to a 2x2x2 pattern. This happens because the Kagome Lattice inverts itself when the temperature gets extremely cold. The new grid it blends into is mostly made up of separate hexagons and triangles, the researchers showed. They also showed how this pattern connects when they take a plane of the RbV3Sb5 structure and rotate it by “looking in” from a different angle.
“It’s like this one Kagome is now becoming these complicated things that split in two,” Mitrovi? called. “It stretches the grid so that the kagome becomes this combination of hexagons and triangles in one layer and then in the next layer, after you rotate it half a circle, it repeats itself.”
Studying this atomic structure is a necessary step to provide a complete picture of the exotic states of matter into which this superconducting material transitions, the researchers said. They believe the results will lead to further investigations into whether this formation and its properties can contribute to superconductivity, or whether it 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 now know what that is, and our next task is to figure out how it relates to other bizarre phases at low temperature – does it help, does it compete, can we control it, can we effect it at higher temperatures, whether.” it is useful?” Mitrovi? called. “Next, we lower the temperature further and learn more.”
The experimental research was led by Jonathan Frassineti, a joint Brown-Bologna University PhD student, Pietro Bonfà from the University of Parma, and two Brown students: Erick Garcia and Rong Cong. The theoretical work was directed by Bonfà while all materials were synthesized at the University of California Santa Barbara. This research included funding from the National Science Foundation.