Spectroscopic fingerprint of chiral Majorana modes at the edge of a quantum anomalous Hall insulator/superconductor heterostructure

Junying Shen; Jian Lyu; Jason Z Gao; Ying-Ming Xie; Chui-Zhen Chen; Chang-Woo Cho; Omargeldi Atanov; Zhijie Chen; Kai Liu; Yajian J Hu; King Yau Yip; Swee K Goh; Qing Lin He; Lei Pan; Kang L Wang; Kam Tuen Law; Rolf Lortz

doi:10.1073/pnas.1910967117

Spectroscopic fingerprint of chiral Majorana modes at the edge of a quantum anomalous Hall insulator/superconductor heterostructure

Proc Natl Acad Sci U S A. 2020 Jan 7;117(1):238-242. doi: 10.1073/pnas.1910967117. Epub 2019 Dec 18.

Authors

Junying Shen¹, Jian Lyu^{1

2}, Jason Z Gao¹, Ying-Ming Xie¹, Chui-Zhen Chen¹, Chang-Woo Cho¹, Omargeldi Atanov¹, Zhijie Chen^{3

4}, Kai Liu^{3

4}, Yajian J Hu⁵, King Yau Yip⁵, Swee K Goh⁵, Qing Lin He^{6

7}, Lei Pan^{6

8

9}, Kang L Wang^{10

8

9}, Kam Tuen Law¹¹, Rolf Lortz¹¹

Affiliations

¹ Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong.
² Department of Physics, Southern University of Science and Technology, 518055 Shenzhen, China.
³ Physics Department, University of California, Davis, CA 95616.
⁴ Physics Department, Georgetown University, Washington, DC 20057.
⁵ Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong.
⁶ Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095.
⁷ International Center for Quantum Materials, School of Physics, Peking University, 100871 Beijing, China.
⁸ Department of Physics, University of California, Los Angeles, CA 90095.
⁹ Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095.
¹⁰ Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095; wang@ee.ucla.edu phlaw@ust.hk lortz@ust.hk.
¹¹ Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong; wang@ee.ucla.edu phlaw@ust.hk lortz@ust.hk.

Abstract

With the recent discovery of the quantum anomalous Hall insulator (QAHI), which exhibits the conductive quantum Hall edge states without external magnetic field, it becomes possible to create a topological superconductor (SC) by introducing superconductivity into these edge states. In this case, 2 distinct topological superconducting phases with 1 or 2 chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers (N) of 1 and 2, respectively. We present spectroscopic evidence from Andreev reflection experiments for the presence of chiral Majorana modes in an Nb/(Cr_0.12Bi_0.26Sb_0.62)₂Te₃ heterostructure with distinct signatures attributed to 2 different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions.

Keywords: Andreev reflection; Majorana fermion; topological superconductivity.