Topological Materials Are Everywhere – New Database Reveals Over 90,000

A new searchable database reveals more than 90,000 known materials with electronic properties that remain unfazed by disturbances. Credit: Christine Daniloff, MIT

The search tool reveals more than 90,000 known materials with electronic properties that remain unfazed by disturbances.

What will it take for our electronic devices to become smarter, faster and more resilient? One idea is to build them from topological materials.

Topology comes from a branch of mathematics that studies shapes that can be manipulated or deformed without losing some essential properties. A donut is a common example: if made of rubber, a donut could be twisted and pressed into a completely new shape, such as a coffee cup, while retaining one key feature – namely, its center hole, which takes the form of the handle of the cup. The hole, in this case, is a topological feature, robust to certain deformations.

In recent years, scientists have applied topology concepts to the discovery of materials with equally robust electronic properties. In 2007, researchers predicted the first electronic topological insulators – materials in which electrons behave “topologically protected” or persistent in the face of certain perturbations.

Since then, scientists have searched for more topological materials in an effort to build better and stronger electronic devices. Until recently, only a handful of these materials had been identified, and so they were assumed to be a rarity.

Now, researchers from MIT and elsewhere have discovered that, in fact, topological materials are everywhere. You just need to know how to look for them.

In an article published on May 20, 2022, in the journal Sciencethe team, led by Nicolas Regnault of princeton university and the École Normale Supérieure Paris, reports harnessing the power of multiple supercomputers to map the electronic structure of more than 96,000 natural and synthetic crystalline materials. They applied sophisticated filters to determine if and what types of topological features exist in each structure.

Overall, they found that 90% of all known crystal structures contain at least one topological property, and more than 50% of all natural materials exhibit some sort of topological behavior.

“We found that there is ubiquity — topology is everywhere,” says Benjamin Wieder, study co-lead and post-doctoral fellow in MIT’s Department of Physics.

The team compiled the newly identified materials into a new Topological Materials database resembling a periodic table of topology. With this new library, scientists can quickly search materials of interest for any topological properties they might hold and exploit them to build ultra-low-power transistors, new magnetic memory storage, and other devices with robust electronic properties.

The article includes co-lead author Maia Vergniory from the Donostia International Physics Center, Luis Elcoro from the University of the Basque Country, Stuart Parkin and Claudia Felser from the Max Planck Institute, and Andrei Bernevig from Princeton University.

Beyond Intuition

The new study was prompted by a desire to accelerate traditional research into topological materials.

“The way the original materials were found was through chemical intuition,” says Wieder. “This approach was very successful at first. But since we had theoretically predicted more types of topological phases, it seemed that intuition didn’t get us very far.

Instead, Wieder and his colleagues used an efficient and systematic method to eliminate signs of topology, or robust electronic behavior, in all known crystal structures, also known as solid-state inorganic materials.

For their study, the researchers turned to the Inorganic Crystal Structure Database, or ICSD, a repository in which researchers enter the atomic and chemical structures of the crystalline materials they studied. The database includes materials found in nature, as well as those that have been synthesized and manipulated in the laboratory. ICSD is currently the largest materials database in the world, containing more than 193,000 crystals whose structures have been mapped and characterized.

The team downloaded the entire ICSD and, after performing data cleaning to eliminate structures containing corrupt files or incomplete data, the researchers were left with just over 96,000 processable structures. For each of these structures, they performed a set of calculations based on fundamental knowledge of the relationship between the chemical constituents, to produce a map of the material’s electronic structure, also known as the electronic band structure.

The team was able to efficiently perform the complicated calculations for each structure using multiple supercomputers, which they then used to perform a second set of operations, this time to track down various known topological phases or persistent electrical behavior in each crystalline material.

“We are looking for signatures in the electronic structure in which certain robust phenomena should occur in this material,” says Wieder, whose previous work involved refining and extending the screening technique, known as topological quantum chemistry.

From their high-throughput analysis, the team quickly discovered a surprisingly large number of materials that are naturally topological, without any experimental manipulation, as well as materials that can be manipulated, for example with light or chemical doping, to exhibit a sort of robust electronic behavior. They also discovered a handful of materials that contained more than one topological state when exposed to certain conditions.

“Topological phases of matter in 3D solid-state materials have been proposed as sites for observing and manipulating exotic effects, including the interconversion of electric current and electron spin, tabletop simulation of exotic theories of high-energy physics, and even, under the right conditions, the storage and manipulation of quantum information,” notes Wieder.

For experimenters studying such effects, Wieder says the team’s new database now reveals a menagerie of new materials to explore.

Reference: “All topological bands of all nonmagnetic stoichiometric materials” by Maia G. Vergniory, Benjamin J. Wieder, Luis Elcoro, Stuart SP Parkin, Claudia Felser, B. Andrei Bernevig and Nicolas Regnault, May 20, 2022, Science.
DOI: 10.1126/science.abg9094

This research was funded, in part, by the US Department of Energy, the National Science Foundation, and the Office of Naval Research.

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