New Way to Identify Correlated Topological Materials

A unique construction principle speculates about the properties of previously unknown quantum materials. For the first time, a strongly correlated topological semimetal has been identified with the help of a computer.

New method to identify strongly correlated topological materials

Silke Bühler-Paschen and Quimiao Si. Credit: © Tommy LaVergne/Rice University

Identifying new materials with specific properties, such as specific electronic properties, required for quantum computing is a complex task. Various compounds in which promising atoms are arranged in specific crystal structures are produced in the low-temperature laboratory at the Vienna University of Technology and the material is then analyzed.

Recently, a collaboration between the Vienna University of Technology, Rice University (Texas) and other international research institutions identified suitable materials on the computer. Novel theoretical methods identified promising candidates from the large number of suitable materials.

Measurements at the Vienna University of Technology showed that the materials have the necessary properties and the process works. This is an important step in quantum materials research. The observations were published in natural physics Diary.

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Topological semimetals

In recent years, the Vienna University of Technology and Rice University in Texas have been searching together for new quantum materials with specific properties. The two research teams presented the first “Weyl-Kondo semimetal” in 2017, a material that could play a crucial role in research into quantum computing technology.

The electrons in such a material cannot be described individually. There are very strong interactions between these electrons, they interfere as waves according to the laws of quantum physics and at the same time repel each other due to their electrical charge.

Silke Bühler-Paschen, Professor, Institute for Solid State Physics, Vienna University of Technology

Due to this strong interaction, which could only be worked out with the help of detailed mathematical methods, the electrons were highly excited.

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Topology – the branch of mathematics concerned with geometric properties that remain unchanged through continuous deformation – also plays an important role in the materials now being evaluated.

If the substance is minimally disturbed, the electronic states in the material can remain stable. This is why these states are so useful in practical applications such as quantum computing.

Using the computer to identify possible candidates

It is not possible to evaluate the behavior of the strongly interacting electrons in a material. No supercomputer anywhere in the world will be able to do that.

Based on the previous findings, it is now possible to generate a design principle that integrates simplified model calculations with mathematical symmetry considerations and uses a database of known materials to suggest which of these materials could exhibit the theoretically expected topological properties.

This method provided three such candidates, and we then made one of these materials and measured it in our lab at low temperatures. And indeed, these first measurements indicate that it is a highly correlated topological semimetal – the first to be predicted on a theoretical basis with a computer.

Silke Bühler-Paschen, Professor, Institute for Solid State Physics, Vienna University of Technology

Creatively exploiting the symmetries of the system was a key to success.

What we postulated was that strongly correlated excitations are still subject to symmetry requirements. Because of this, I can say a lot about the topology of a system without resorting to ab initio calculations, which are often required but particularly challenging for the study of highly correlated materials. Everything indicates that we have found a robust way to identify materials with the properties we want.

Qimiao Si, Rice University

magazine reference

Chen, L. et al. (2022) Topological semimetal driven by strong correlations and crystalline symmetry. natural physics.

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