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Exotic "topological" materials are surprisingly common

As part of a major breakthrough in a field of research that won the 2016 Nobel Prize in Physics, an international team discovered that substances with an exotic electronic behavior, called topological materials, are actually quite common and include daily items such as arsenic and gold. The team created an online catalog to facilitate the design of new topological materials using periodic table elements.

These materials have unexpected and strange properties that have changed scientists' understanding of the behavior of electrons. The researchers hope that these substances could form the basis of future technologies, such as low power devices and quantum computing.

"Once the analysis was completed and all the errors corrected, the result was astonishing: more than a quarter of all materials have some kind of topology," said B. Andrei Bernevig, lead author of the journal and professor of physics at Princeton. "The topology is ubiquitous in materials, not esoteric."

Topological materials intrigue because their surfaces can conduct electricity without resistance and are therefore potentially faster and more energy efficient than current technologies. Their name comes from an underlying theory that relies on topology, a branch of mathematics that describes objects according to their ability to be stretched or folded.

The beginnings of the theoretical understanding of these states of matter were at the root of the 2016 Nobel Prize in Physics, shared by Professor F. Duncan Haldane of Princeton University, the professor of physics at the University of Princeton. Sherman Fairchild University, J. Michael Kosterlitz of Brown University and David J. Thouless, University of Washington, Seattle.

The topological material database allows users to select items in the period table to create a compound that can then be explored for topological properties. Credit: Maia G. Vergniory, Luis Elcoro, Claudia Felser, Nicolas Regnault, B. Andrei Bernevig and Zhijun Wang

Until now, only a few hundred of the more than 200,000 known inorganic crystalline materials have been termed topological, and it was thought that they were anomalies.

"Once completed, this catalog will usher in a new era for the design of topological materials," said Bernevig. "This is the beginning of a new type of periodic table where compounds and elements are indexed according to their topological properties rather than by more traditional means."

The international team included Princeton researchers; the Donostia International Center for Physics in San Sebastián, Spain; the Basque IKERBASQUE foundation for science; the University of the Basque Country; Ecole Normale Supérieure Paris and the French National Center for Scientific Research; and the Max Planck Institute for Solid Chemical Physics.

The team has studied about 25,000 inorganic materials whose atomic structures are experimentally known accurately and classified in the inorganic crystal structure database. The results show that rather than being rare, over 27% of the materials in nature are topological.

The newly created database allows visitors to select items in the periodic table to create compounds that the user can then explore for its topological properties. More materials are being analyzed and placed in a database for future publication.

Two factors allowed the complex task of topologically classifying the 25,000 compounds.

First, two years ago, some of the authors present developed a theory, known as topological quantum chemistry and published in Nature in 2017, which made it possible to classify the topological properties of any material from the simple knowledge of the positions and the nature of its atoms.

Second, in the current study, the team applied this theory to the compounds of the inorganic crystal structure database. In doing so, the authors had to design, write and modify a large number of computerized instructions to calculate the energy of electrons in materials.

"We had to use these old programs and add new modules to calculate the required electronic properties," said Zhijun Wang, a postdoctoral fellow at Princeton, who is currently a professor at the Beijing National Laboratory of Condensed Matter Physics. Institute of Physics, Chinese Academy of Sciences.

"We then had to analyze these results and calculate their topological properties based on our new methodology of topological quantum chemistry," said Luis Elcoro, a professor at the University of the Basque Country of Bilbao, Spain.

The authors have written several sets of codes for obtaining and analyzing the topology of electrons in real materials. The authors made these codes available to the public via the Bilbao Crystallography Server. With the help of the Max Planck Supercomputer Center in Garching, Germany, the researchers then performed their codes on the 25,000 compounds.

"On the IT front, it was very intensive," said Nicolas Regnault, professor at the Ecole Normale Supérieure in Paris and director of research at the CNRS. "Fortunately, the theory has shown us that we need to calculate only a fraction of the data we needed before." We need to look at what the "electron" does "only in one part of the world." parameters space to get the topology of the system. "

"This classification has allowed us to better understand the materials," said Maia Garcia Vergniory, a researcher at the Donostia International Physics Center in San Sebastián, Spain. "It's really the last line of understanding the properties of materials."

Claudia Felser, a professor at the Max Planck Institute for Solid State Chemical Physics in Dresden, Germany, previously predicted that even gold is topological. "Many of the material properties we know, such as the color of gold – can be understood through topological reasoning," said Felser.

The team is currently working on the classification of the topological nature of additional compounds in the database. The next steps are to identify compounds with the best versatility, conductivity, and other properties, and experimentally verify their topological nature. "One can then dream of a complete topological periodic table," Bernevig said.

The study "A complete catalog of topological materials of high quality". By Mr. G. Vergniory, L. Elcoro, Claudia Felser, Nicolas Regnault, B. Andrei Bernevig and Zhijun Wang, was published online in the journal Nature February 28, 2019.

Explore further:
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More information:
A complete catalog of topological materials of high quality, Nature (2019). DOI: 10.1038 / s41586-019-0954-4, https://www.nature.com/articles/s41586-019-0954-4

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Princeton University

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