Title: Topological crystalline insulator states in the Ca₂As family

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. Here, 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. Moreover, the other family members, including Ca₂Sb, Ca₂Bi, and Sr₂Sb, feature different topological surface states due to their distinct topological invariants. We thus further propose topological phase transitions in the pseudobinary systems such as (Ca_1–xSr_x)₂As and Ca₂As_xSb_1–x. Our work reveals rich and exotic TCI physics across the Ca₂As family of materials and demonstrates a complete roadmap for uncoveringmore » TCIs topological nature based on first-principles calculations. Such a method can be broadly applied in searching for new TCIs.« less

Authors:

Zhou, Xiaoting ^[1]; Hsu, Chuang-Han ^[2]; Chang, Tay-Rong ^[1]; Tien, Hung-Ju ^[1]; Ma, Qiong ^[3]; Jarillo-Herrero, Pablo ^[3]; Gedik, Nuh ^[3]; Bansil, Arun ^[4]; Pereira, Vitor M. ^[2]; Xu, Su-Yang ^[3]; Lin, Hsin ^[5]; Fu, Liang ^[3]

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+ Show Author Affiliations

1. National Cheng Kung Univ., Tainan City (Taiwan)
2. National University of Singapore (Singapore)
3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
4. Northeastern Univ., Boston, MA (United States)
5. Academia Sinica, Taipei (Taiwan)

Publication Date:

Tue Dec 04 00:00:00 EST 2018

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Center for Excitonics (CE); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; US Air Force Office of Scientific Research (AFOSR); Gordon and Betty Moore Foundation; Ministry of Science and Technology (MOST); National Center for Theoretical Sciences (NCTS); USDOE

OSTI Identifier:

1544152

Alternate Identifier(s):

OSTI ID: 1484420

Grant/Contract Number:  

SC0010526; SC0001088; FA9550-16-1-0382; GBMF4541; GBMF4540; FG02-07ER46352; AC02-05CH11231; MOST107-2636-M-006-004; DESC0001088

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B

Additional Journal Information:

Journal Volume: 98; Journal Issue: 24; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY