Scientists are constantly searching for new materials called topological insulators, due to their unique ability to insulate on the inside but conduct electrical current on their surface. This property allows an electrical current to theoretically flow without resistance and respond in unconventional ways to electric and magnetic fields.
Recently, a team of researchers made an unexpected discovery in this field that proves that the widely used material bismuth is one among myriad topological insulating materials that hadn’t been identified before. This work is a big step forward for finding new materials to replace silicon in fields like quantum computers and high-performance electronics.
“We discovered thousands of new topological materials,” Maia G. Vergniory, Ikerbasque researcher at the Donostia International Physics Center at the University of the Basque Country (UPV/EHU), told Design News. “Our work proves there are much more than we thought,” she said.
Vergniory worked alongside researchers at Princeton University and Max Planck Institute of Microstructure Physics to make the discovery of these materials, which researchers call “higher-order topological insulators.”
While some of the materials have average capabilities in terms of electrical conductivity, some have capabilities that far exceeded researchers’ expectation for the materials. Bismuth—already used as a substitute for lead in myriad applications—is one of those materials. Now, it and the other materials discovered by Vergniory and her team also may become alternatives to silicon, she said. “Silicon has reached its limits and it's very environmentally unfriendly because it consumes a lot of energy.”
Researchers’ theoretical studies proved that for a material to be a higher-order topological insulator, its conducting edges must be extraordinarily robust. This means that the current of topological electrons cannot be stopped by impurities and—if the crystal breaks—the new edges automatically must conduct current.
What the team discovered about the new materials, including bismuth, is that they can in theory conduct electricity without any dissipation—just as superconductors do at low temperatures.
“They have very robust electronic channels at room temperature and at a microscopic size,” Vergniory explained.
Researchers used a number of techniques to verify the materials as high-order topological insulators. The first identified them by using symmetry arguments, topological indices, first-principles calculations, and a relatively new method—a framework of topological quantum chemistry.
Following theoretical verification, researchers then conducted experiments to identify the materials. Using scanning-tunneling spectroscopy, they proved the unique signatures of the rotational symmetry of the one-dimensional states located at step edges of the crystal surface. They also used what’s called Josephson interferometry to demonstrate their universal topological contribution to the electronic transport. The team, which also included scientists from Paris-Sud University and Centro National de la Recherche Scientifique, published a paper on their work in the journal Nature Physics.
Researchers plan to continue their work by further investigating the magnetic interactions in the new topological insulators they’ve identified, Vergniory said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time, she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.
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