Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices

Journal Article · 01 January 2020 · Science

DOI: https://doi.org/10.1126/science.aax6361 · OSTI ID:1580806

Kayyalha, Morteza ; Xiao, Di ; Zhang, Ruoxi ; Shin, Jaeho ; Jiang, Jue; Wang, Fei; Zhao, Yi-Fan; Xiao, Run; Zhang, Ling; Fijalkowski, Kajetan M. ; Mandal, Pankaj; Winnerlein, Martin; Gould, Charles; Li, Qi ; Molenkamp, Laurens W. ; Chan, Moses H. W. ; Samarth, Nitin ; Chang, Cui-Zu

A quantum anomalous Hall (QAH) insulator coupled to an s-wave superconductor is predicted to harbor chiral Majorana modes. A recent experiment interprets the half-quantized two-terminal conductance plateau as evidence for these modes in a millimeter-size QAH-niobium hybrid device. However, non-Majorana mechanisms can also generate similar signatures, especially in disordered samples. Here, we studied similar hybrid devices with a well-controlled and transparent interface between the superconductor and the QAH insulator. When the devices are in the QAH state with well-aligned magnetization, the two-terminal conductance is always half-quantized. Our experiment provides a comprehensive understanding of the superconducting proximity effect observed in QAH-superconductor hybrid devices and shows that the half-quantized conductance plateau is unlikely to be induced by chiral Majorana fermions in samples with a highly transparent interface.

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0019064
• OSTI ID: 1580806
• Alternate ID(s): OSTI ID: 1803543
• Journal Information: Science, Journal Name: Science Journal Issue: 6473 Vol. 367; ISSN 0036-8075
• Publisher: American Association for the Advancement of Science (AAAS)Copyright Statement
• Country of Publication: United States
• Language: English