期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 116, 期 27, 页码 13255-13259出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1900527116
关键词
topological crystalline insulator; bismuth; topological hinge states; electronic structure
资金
- Young Scholar Fellowship Program from the Ministry of Science and Technology (MOST) in Taiwan, under a MOST grant for the Columbus Program [MOST108-2636M-006-002]
- National Cheng Kung University, Taiwan
- National Center for Theoretical Sciences, Taiwan
- MOST, Taiwan [MOST107-2627-E-006-001]
- Higher Education Sprout Project, Ministry of Education
- Academia Sinica, Taiwan under Innovative Materials and Analysis Technology Exploration [AS-iMATE107-11]
- US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering [DE-SC0018945]
- US DOE, Office of Science, BES [DE-FG02-07ER46352]
- DOE [DE-AC02-05CH11231]
- Science and Technology Center for Integrated Quantum Materials, NSF [DMR-1231319]
Bismuth-based materials have been instrumental in the development of topological physics, even though bulk bismuth itself has been long thought to be topologically trivial. A recent study has, however, shown that bismuth is in fact a higher-order topological insulator featuring one-dimensional (1D) topological hinge states protected by threefold rotational and inversion symmetries. In this paper, we uncover another hidden facet of the band topology of bismuth by showing that bismuth is also a first-order topological crystalline insulator protected by a twofold rotational symmetry. As a result, its (1 (1) over bar0) surface exhibits a pair of gapless Dirac surface states. Remarkably, these surface Dirac cones are unpinned in the sense that they are not restricted to locate at specific k points in the (1 (1) over bar0) surface Brillouin zone. These unpinned 2D Dirac surface states could be probed directly via various spectroscopic techniques. Our analysis also reveals the presence of a distinct, previously uncharacterized set of 1D topological hinge states protected by the twofold rotational symmetry. Our study thus provides a comprehensive understanding of the topological band structure of bismuth.
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