Topological crystalline insulator states in the Ca<sub>2</sub>As family

ORAL

Abstract

Topological crystalline insulators (TCIs) are insulating electronic phases of matter with nontrivial topology originating from crystalline symmetries. Recent theoretical advances have proposed new TCI states protected by rotational symmetries and provided powerful guidelines to search for TCIs in real materials. Building upon recent theoretical works, we demonstrate a feasible method to identify new TCI states based on first-principles calculations.We systematically unveil the topological properties of the TCI states in Ca2As. On both top and side surfaces, we observe topological surface states protected independently by rotational and mirror symmetries.We show that a particular lattice distortion can single out the newly proposed topological protection by the rotational symmetry. As a result, the Dirac points of the topological surface states are moved to generic locations in momentum space away from any high-symmetry lines. Such topological surface states have not been seen before. Our work reveals rich and exotic TCI physics across the Ca2As family of materials and demonstrates a complete roadmap for uncovering TCIs topological nature based on first-principles calculations. Such a method can be broadly applied in searching for new TCIs.

–

Presenters

  • XIAOTING ZHOU

    • Physics, National Cheng Kung University, Tainan, 701, Taiwan
    • National Cheng Kung University
    • Department of Physics, National Cheng Kung University

Authors

  • XIAOTING ZHOU

    • Physics, National Cheng Kung University, Tainan, 701, Taiwan
    • National Cheng Kung University
    • Department of Physics, National Cheng Kung University

  • Chuang-Han Hsu

    • Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore
    • National University of Singapore
    • Physics, National University of Singapore

  • Tay-Rong Chang

    • National Cheng Kung University
    • Physics, National Cheng Chung University
    • Physics, National Cheng Kung University, Tainan, 701, Taiwan
    • Department of Physics, National Cheng Kung University
    • Physics, National Tsing Hua University
    • Physics, National Cheng Kung University

  • Qiong Ma

    • Massachusetts Institute of Technology
    • Department of Physics, Massachusetts Institute of Technology

  • Pablo Jarillo-Herrero

    • Physics, Massachusetts Institute of Technology
    • Department of Physics, Massachusetts Institute of Technology
    • Massachusetts Institute of Technology
    • Dept. of Physics, Massachusetts Institute of Technology, USA
    • Massachusetts Inst of Tech-MIT
    • Physics, MIT

  • Nuh Gedik

    • Physics, Massachusetts Institute of Technology
    • Massachusetts Inst of Tech-MIT
    • Massachusetts Institute of Technology
    • Department of Physics, Massachusetts Institute of Technology

  • Arun Bansil

    • Northeastern University
    • Department of Physics, Northeastern University

  • Vitor Pereira

    • Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
    • National University of Singapore
    • Department of Physics, National University of Singapore
    • Centre for Advanced 2D Materials, National University of Singapore

  • Suyang Xu

    • Department of Physics, Massachusetts Institute of Technology
    • Massachusetts Institute of Technology
    • MIT
    • Physics, MIT
    • Department of Physics, Massachusetts Institute of Technology, Cambridge

  • Hsin Lin

    • Academia Sinica
    • Institute of Physics, Academia Sinica
    • Physics, Academia Sinica, Taipei 11529, Taiwan
    • Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
    • Physics, Academia Sinica
    • Department of Physics, National University of Singapore
    • National University of Singapore
    • Academia Sinica, Taipei, Taiwan

  • Liang Fu

    • Massachusetts Institute of Technology
    • MIT
    • Department of Physics, Massachusetts Institute of Technology