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

Abstract

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.

Authors:
ORCiD logo; ORCiD logo; ORCiD logo; ORCiD logo; ; ; ; ; ; ORCiD logo; ; ; ; ORCiD logo; ORCiD logo; ORCiD logo; ORCiD logo; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1580806
Grant/Contract Number:  
SC0019064; FG01-08ER46531; project 3-TOP and 4TOPS
Resource Type:
Published Article
Journal Name:
Science
Additional Journal Information:
Journal Name: Science Journal Volume: 367 Journal Issue: 6473; Journal ID: ISSN 0036-8075
Publisher:
American Association for the Advancement of Science (AAAS)
Country of Publication:
United States
Language:
English

Citation Formats

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, and Chang, Cui-Zu. Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices. United States: N. p., 2020. Web. doi:10.1126/science.aax6361.
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. Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices. United States. doi:10.1126/science.aax6361.
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, and Chang, Cui-Zu. Thu . "Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices". United States. doi:10.1126/science.aax6361.
@article{osti_1580806,
title = {Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices},
author = {Kayyalha, Morteza and Xiao, Di and Zhang, Ruoxi and Shin, Jaeho and Jiang, Jue and Wang, Fei and Zhao, Yi-Fan and Xiao, Run and Zhang, Ling and Fijalkowski, Kajetan M. and Mandal, Pankaj and Winnerlein, Martin and Gould, Charles and Li, Qi and Molenkamp, Laurens W. and Chan, Moses H. W. and Samarth, Nitin and Chang, Cui-Zu},
abstractNote = {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.},
doi = {10.1126/science.aax6361},
journal = {Science},
number = 6473,
volume = 367,
place = {United States},
year = {2020},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
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DOI: 10.1126/science.aax6361

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