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

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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 0.12 Bi 0.26 Sb 0.62 ) 2 Te 3 heterostructure with distinct signatures attributed to 2 different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions.
Funding Information
  • Research Grants Council, University Grants Committee (GRF-16302018, SBI17SC14, IEG16SC03)
  • Research Grants Council, University Grants Committee (C6026-16W)
  • Croucher Foundation (N.A.)
  • Tai-chin Lo Foundation (N.A.)
  • ARO Multiple University Research Initiative (N.A.)
  • Energy Frontier Research Center (N.A.)
  • National Natural Science Foundation of China (11874070)
  • National Key R&D Program of China (Grant 338 No. 2018YFA0305601)
  • National Thousand-Young Talents Program in China (N.A.)
  • US National Science Foundation (DMR-1610060)

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