Physicists' demonstrative method for designing topological metals

Physicists’ demonstrative method for designing topological metals

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American and European physicists have demonstrated a new method to predict whether metallic compounds are likely to host topological states arising from strong interactions with electrons.

Physicists from Rice University, leading the research and collaborating with physicists from Stony Brook University, the Vienna University of Technology (TU Wien), Los Alamos National Laboratory, the International Center for Physics in Spain Donostia, and the Max Planck Institute for Chemical Physics of Solids in Germany, have revealed their new design principle in a study published online today in The physics of nature.

The team includes scientists from Rice, TU Wien and Los Alamos who discovered the first strongly correlated topological semimetal in 2017. This system and others that the new design principle seeks to identify are widely sought after by the quantum computing industry, because topological states have immutable characteristics that cannot. be erased or lost due to quantum decoherence.

“The landscape of strongly correlated topological matter is both large and largely unexplored,” said study co-author Qimiao Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice. “We expect this work will help guide its exploration.”

In 2017, Si’s research group at Rice conducted a model study and found a surprising state of matter that hosted both topological character and a key example of strong correlation physics called the Kondo effect, an interaction between moments magnetic fields of correlated electrons confined to atoms in a metal and the collective spins of billions of transient conduction electrons. At the same time, an experimental team led by Silke Paschen from TU Wien introduced a new material and reported that it has the same properties as the theoretical solution. The two teams called the strongly correlated state of semimetallic matter Weyl-Kondo. Si said that crystal symmetry played an important role in the studies, but the analysis remained at the proof-of-principle level.

“Our work in 2017 focused on a kind of hydrogen atom with crystal symmetry,” said Si, a theoretical physicist who has spent more than two decades studying strongly correlated materials such as heavy fermions and unconventional superconductors. “But it set the stage for the design of a new correlated metal topology.”

Strongly correlated quantum materials are those in which the interactions of billions and billions of electrons give rise to collective behaviors, such as unconventional superconductivity, or electrons behaving as if they had more than 1,000 times their normal mass. Although physicists have studied topological materials for decades, they have only recently begun to investigate topological metals that host strongly correlated interactions.

“Designing materials is very hard in general, and designing strongly correlated materials is even harder,” said Si, a member of the Rice Quantum Initiative and director of the Rice Center for Quantum Materials (RCQM).

Jennifer Cano of Si and Stony Brook led a group of theorists who developed a framework for identifying promising candidate materials by cross-referencing information from a database of known materials with the output of theoretical calculations based on realistic crystal structures. Using the method, the group identified the crystal structure and elemental composition of three materials that were likely candidates for hosting topological states arising from the Kondo effect.

“Since we developed the theory of topological quantum chemistry, it has been a long-standing goal to apply the formalism to strongly correlated materials,” said Cano, assistant professor of physics and astronomy at Stony Brook and researcher at the Flatiron Institute’s Computing Center. Quantum physics. “Our work is the first step in that direction.”

Si said the predictive theoretical framework resulted from a realization he and Cano had following an impromptu discussion session they held among their working groups at the Aspen Center for Physics in 2018.

“What we postulated was that strongly correlated excitations are still subject to symmetry requirements,” he said. “Because of this, they can tell a lot about the topology of a system without resorting to ab initio calculations that are often necessary but are particularly difficult for the study of strongly correlated materials.”

To test the hypothesis, theorists at Rice and Stony Brook conducted model studies for realistic crystal symmetries. During the pandemic, the theoretical teams in Texas and New York had extensive virtual discussions with Paschen’s experimental group at TU Wien. The collaboration developed the design principle for correlated topological-semimetallic materials with the same symmetries as those used in the studied model. The utility of the design principle was demonstrated by Paschen’s team, who made one of the three identified compounds, tested it, and verified that it harbored the predicted properties.

“All indications are that we have found a robust way to identify materials that have the characteristics we want,” Si said.

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More information:
Silke Paschen, Topological Semimetal Driven by Strong Correlations and Crystal Symmetry, The physics of nature (2022). DOI: 10.1038/s41567-022-01743-4.

Provided by Rice University

Citation: Physicists’ Demo Method for Designing Topological Metals (2022, September 15) Retrieved September 20, 2022, from

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