Physicists demonstration method for designing topological metals

HOUSTON, TX – US and European physicists have demonstrated a new method to predict whether metallic compounds are likely to harbor topological states resulting from strong electronic interactions.

Physicists from Rice University, leading the research and collaborating with physicists from Stony Brook University, Vienna University of Technology in Austria (TU Wien), Los Alamos National Laboratory, International Center for Physics of Donostia in Spain and Germany’s Max Planck Institute for Chemical Solid State Physics, unveiled their new design principle in a study published online in Natural Physics.

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 industry. of quantum computing because topological states have immutable characteristics that cannot be erased or lost due to quantum decoherence.

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

In 2017, Si’s research group at Rice performed a model study and discovered a startling state of matter that harbored both a topological character and a quintessential example of highly correlated physics called the Kondo effect, an interaction between the magnetic moments of correlated electrons confined to atoms in a metal and the collective spins of billions of passing conduction electrons. At the same time, an experimental team led by Silke Paschen from TU Wien introduced a new material and reported that it had the same properties as the theoretical solution. The two teams named the strongly correlated state of matter a Weyl-Kondo semimetal. Si said 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 crystal-symmetry hydrogen atom,” said Si, a theoretical physicist who has spent more than two decades studying strongly correlated materials like heavy fermions and non-superconductors. conventional. “But it paved the way for the design of a new correlated metallic topology.”

Strongly correlated quantum materials are those where the interactions of billions upon billions of electrons give rise to collective behaviors like unconventional superconductivity or electrons that behave as if they have more than 1,000 times their normal mass. Although physicists have studied topological materials for decades, they have only recently begun to study topological metals that harbor strongly correlated interactions.

“Designing materials is very difficult in general, and designing strongly correlated materials is even more difficult,” 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 to identify promising candidate materials by cross-referencing information in 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 may harbor topological states resulting from the Kondo effect.

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

Si said the predictive theoretical framework stemmed from a realization he and Cano had from an impromptu chat session they held between their respective work groups at the Aspen Center for Physics in 2018.

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

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

“Everything indicates that we’ve found a robust way to identify materials that have the characteristics we want,” Si said.

Study co-authors include Rice’s Lei Chen, Chandan Setty and Haoyu Hu; Sarah Grefe ’17, Rice alumnus, Los Alamos National Laboratory; Lukas Fischer, Xinlin Yan, Gaku Eguchi and Andrey Prokofiev from TU Wien; and Maia Vergniory of the Max Planck Institute for Solid-State Chemical Physics in Dresden, Germany, and the Donostia International Physics Center in San Sebastian, Spain.

– This press release originally appeared on the Rice University website

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