期刊
ADVANCED MATERIALS
卷 32, 期 14, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.201907565
关键词
axion insulator; condensed matter physics; higher order topological insulator; magnetic Dirac semimetal
类别
资金
- Ministry of Science and Technology of China [2016YFA0300600, 2016YFA0401000, 2017YFA0302901]
- National Natural Science Foundation of China [11622435, 11474340, 11474330, 11674369, 11422428]
- Sino-Swiss Science and Technology Cooperation [IZLCZ2-170075]
- NCCR-MARVEL - Swiss National Science Foundation
- Swiss National Science Foundation [200021_182695]
- Chinese Academy of Sciences [XDB07000000, QYZDB-SSW-SLH043]
- K. C. Wong Education Foundation [GJTD-2018-01]
- Beijing Municipal Science & Technology Commission [Z171100002017018]
- CAS Pioneer Hundred Talents Program (type C)
- U.S. Department of Energy (DOE) [DESC0002623]
- National Science Foundation [ACI-1548562]
- Canada First Research Excellence Fund
- Swiss National Science Foundation (SNF) [200021_182695] Funding Source: Swiss National Science Foundation (SNF)
Parity-time symmetry plays an essential role for the formation of Dirac states in Dirac semimetals. So far, all of the experimentally identified topologically nontrivial Dirac semimetals (DSMs) possess both parity and time reversal symmetry. The realization of magnetic topological DSMs remains a major issue in topological material research. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, it is ascertained that band inversion induces a topologically nontrivial ground state in EuCd2As2. As a result, ideal magnetic Dirac fermions with simplest double cone structure near the Fermi level emerge in the antiferromagnetic (AFM) phase. The magnetic order breaks time reversal symmetry, but preserves inversion symmetry. The double degeneracy of the Dirac bands is protected by a combination of inversion, time-reversal, and an additional translation operation. Moreover, the calculations show that a deviation of the magnetic moments from the c-axis leads to the breaking of C3 rotation symmetry, and thus, a small bandgap opens at the Dirac point in the bulk. In this case, the system hosts a novel state containing three different types of topological insulator: axion insulator, AFM topological crystalline insulator (TCI), and higher order topological insulator. The results provide an enlarged platform for the quest of topological Dirac fermions in a magnetic system.
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