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Emergence of nontrivial low‐energy dirac fermions in antiferromagnetic EuCd 2 As 2

DOI: 10.1002/adma.201907565 DOI Help

Authors: Junzhang Ma (Swiss Light Source; École Polytechnique Fédérale de Lausanne) , Han Wang (Rensselaer Polytechnic Institute) , Simin Nie (Stanford University) , Changjiang Yi (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences) , Yuanfeng Xu (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences) , Hang Li (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences) , Jasmin Jandke (Swiss Light Source) , Wulf Wulfhekel (Karlsruhe Institute of Technology) , Yaobo Huang (Shanghai Synchrotron Radiation Faciity) , Damien West (Rensselaer Polytechnic Institute) , Pierre Richard (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences; Université de Sherbrooke) , Alla Chikina (Swiss Light Source) , Vladimir N. Strocov (Swiss Light Source) , Joël Mesot (Swiss Light Source; École Polytechnique Fédérale de Lausanne) , Hongming Weng (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; Songshan Lake Materials Laboratory Dongguan) , Shengbai Zhang (Rensselaer Polytechnic Institute) , Youguo Shi (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; Songshan Lake Materials Laboratory Dongguan) , Tian Qian (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; Songshan Lake Materials Laboratory Dongguan) , Ming Shi (Swiss Light Source) , Hong Ding (Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences; Songshan Lake Materials Laboratory Dongguan)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Materials , VOL 5

State: Published (Approved)
Published: February 2020
Diamond Proposal Number(s): 17080

Abstract: 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.

Journal Keywords: axion insulator; condensed matter physics; higher order topological insulator; magnetic Dirac semimetal

Subject Areas: Materials, Physics


Instruments: I05-ARPES

Other Facilities: Shanghai Synchrotron Radiation Facility (SSRF); Swiss Light Source (PSI); BESSY