Premium
Emergence of Nontrivial Low‐Energy Dirac Fermions in Antiferromagnetic EuCd 2 As 2
Author(s) -
Ma Junzhang,
Wang Han,
Nie Simin,
Yi Changjiang,
Xu Yuanfeng,
Li Hang,
Jandke Jasmin,
Wulfhekel Wulf,
Huang Yaobo,
West Damien,
Richard Pierre,
Chikina Alla,
Strocov Vladimir N.,
Mesot Joël,
Weng Hongming,
Zhang Shengbai,
Shi Youguo,
Qian Tian,
Shi Ming,
Ding Hong
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201907565
Subject(s) - topological insulator , physics , dirac fermion , parity (physics) , topological order , antiferromagnetism , condensed matter physics , point reflection , topology (electrical circuits) , fermion , semimetal , quantum mechanics , band gap , quantum , mathematics , combinatorics
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 EuCd 2 As 2 . 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.