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Title: Zero-bias conductance peak in Dirac semimetal-superconductor devices

Abstract

Majorana zero modes (MZMs), fundamental building blocks for realizing topological quantum computers, can appear at the interface between a superconductor and a topological material. One of the experimental signatures that has been widely pursued to confirm the existence of MZMs is the observation of a large, quantized zero-bias conductance peak (ZBCP) in the differential conductance measurements. In this Letter, we report observation of such a large ZBCP in junction structures of normal metal (titanium/gold Ti/Au)—Dirac semimetal (cadmium-arsenide Cd3As2)—conventional superconductor (aluminum Al), with a value close to four times that of the normal state conductance. Our detailed analyses suggest that this large ZBCP is most likely not caused by MZMs. We attribute the ZBCP, instead, to the existence of a supercurrent between two far-separated superconducting Al electrodes, which shows up as a zero-bias peak because of the circuitry and thermal fluctuations of the supercurrent phase, a mechanism conceived by Ivanchenko and Zil'berman more than 50 years ago [Ivanchenko and Zil’berman, JETP 28, 1272 (1969)]. Our results thus call for extreme caution when assigning the origin of a large ZBCP to MZMs in a multiterminal semiconductor or topological insulator/semimetal setup. We thus provide criteria for identifying when the ZBCP is definitely notmore » caused by an MZM. Furthermore, we present several remarkable experimental results of a supercurrent effect occurring over unusually long distances and clean perfect Andreev reflection features.« less

Authors:
; ORCiD logo; ; ; ORCiD logo; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); ARO
OSTI Identifier:
1635577
Alternate Identifier(s):
OSTI ID: 1644080
Report Number(s):
SAND-2020-7280J
Journal ID: ISSN 2643-1564; PPRHAI; 032002
Grant/Contract Number:  
NA0003525; AC04-94AL85000; W911NF-18-1-0416; DMR-1921581
Resource Type:
Published Article
Journal Name:
Physical Review Research
Additional Journal Information:
Journal Name: Physical Review Research Journal Volume: 2 Journal Issue: 3; Journal ID: ISSN 2643-1564
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Topological materials; dirac semimetal; Josephson junctions

Citation Formats

Yu, W., Haenel, Rafael, Rodriguez, M. A., Lee, S. R., Zhang, F., Franz, M., Pikulin, D. I., and Pan, W. Zero-bias conductance peak in Dirac semimetal-superconductor devices. United States: N. p., 2020. Web. https://doi.org/10.1103/PhysRevResearch.2.032002.
Yu, W., Haenel, Rafael, Rodriguez, M. A., Lee, S. R., Zhang, F., Franz, M., Pikulin, D. I., & Pan, W. Zero-bias conductance peak in Dirac semimetal-superconductor devices. United States. https://doi.org/10.1103/PhysRevResearch.2.032002
Yu, W., Haenel, Rafael, Rodriguez, M. A., Lee, S. R., Zhang, F., Franz, M., Pikulin, D. I., and Pan, W. Wed . "Zero-bias conductance peak in Dirac semimetal-superconductor devices". United States. https://doi.org/10.1103/PhysRevResearch.2.032002.
@article{osti_1635577,
title = {Zero-bias conductance peak in Dirac semimetal-superconductor devices},
author = {Yu, W. and Haenel, Rafael and Rodriguez, M. A. and Lee, S. R. and Zhang, F. and Franz, M. and Pikulin, D. I. and Pan, W.},
abstractNote = {Majorana zero modes (MZMs), fundamental building blocks for realizing topological quantum computers, can appear at the interface between a superconductor and a topological material. One of the experimental signatures that has been widely pursued to confirm the existence of MZMs is the observation of a large, quantized zero-bias conductance peak (ZBCP) in the differential conductance measurements. In this Letter, we report observation of such a large ZBCP in junction structures of normal metal (titanium/gold Ti/Au)—Dirac semimetal (cadmium-arsenide Cd3As2)—conventional superconductor (aluminum Al), with a value close to four times that of the normal state conductance. Our detailed analyses suggest that this large ZBCP is most likely not caused by MZMs. We attribute the ZBCP, instead, to the existence of a supercurrent between two far-separated superconducting Al electrodes, which shows up as a zero-bias peak because of the circuitry and thermal fluctuations of the supercurrent phase, a mechanism conceived by Ivanchenko and Zil'berman more than 50 years ago [Ivanchenko and Zil’berman, JETP 28, 1272 (1969)]. Our results thus call for extreme caution when assigning the origin of a large ZBCP to MZMs in a multiterminal semiconductor or topological insulator/semimetal setup. We thus provide criteria for identifying when the ZBCP is definitely not caused by an MZM. Furthermore, we present several remarkable experimental results of a supercurrent effect occurring over unusually long distances and clean perfect Andreev reflection features.},
doi = {10.1103/PhysRevResearch.2.032002},
journal = {Physical Review Research},
number = 3,
volume = 2,
place = {United States},
year = {2020},
month = {7}
}

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