Higher-Order Topology in Bismuth

The mathematical field of topology has become a framework to describe the low-energy electronic structure of crystalline solids. A typical feature of a bulk insulating three-dimensional topological crystal are conducting two-dimensional surface states. This constitutes the topological bulk-boundary...

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Vydáno v:Nature physics Ročník 14; číslo 9; s. 918 - 924
Hlavní autoři: Schindler, Frank, Wang, Zhijun, Vergniory, Maia G, Cook, Ashley M, Murani, Anil, Sengupta, Shamashis, Kasumov, Alik Yu, Deblock, Richard, Jeon, Sangjun, Drozdov, Ilya, Bouchiat, Hélène, Guéron, Sophie, Yazdani, Ali, Bernevig, B Andrei, Neupert, Titus
Médium: Journal Article
Jazyk:angličtina
Vydáno: England Nature Publishing Group 01.09.2018
Témata:
Bismuth
Crystal surfaces
Electron transport
Electronic structure
First principles
Interferometry
Organic chemistry
Quantum chemistry
Rotational spectra
Symmetry
Theoretical analysis
Topology
ISSN:1745-2473, 1745-2481
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Shrnutí:The mathematical field of topology has become a framework to describe the low-energy electronic structure of crystalline solids. A typical feature of a bulk insulating three-dimensional topological crystal are conducting two-dimensional surface states. This constitutes the topological bulk-boundary correspondence. Here, we establish that the electronic structure of bismuth, an element consistently described as bulk topologically trivial, is in fact topological and follows a generalized bulk-boundary correspondence of higher-order: not the surfaces of the crystal, but its hinges host topologically protected conducting modes. These hinge modes are protected against localization by time-reversal symmetry locally, and globally by the three-fold rotational symmetry and inversion symmetry of the bismuth crystal. We support our claim theoretically and experimentally. Our theoretical analysis is based on symmetry arguments, topological indices, first-principle calculations, and the recently introduced framework of topological quantum chemistry. We provide supporting evidence from two complementary experimental techniques. With scanning-tunneling spectroscopy, we probe the unique signatures of the rotational symmetry of the one-dimensional states located at step edges of the crystal surface. With Josephson interferometry, we demonstrate their universal topological contribution to the electronic transport. Our work establishes bismuth as a higher-order topological insulator.
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ISSN:1745-2473
1745-2481
DOI:10.1038/s41567-018-0224-7