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Title: Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor

Abstract

Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s±, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the c-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.

Authors:
ORCiD logo [1];  [1];  [2];  [1];  [1];  [1];  [1];  [1];  [3];  [4];  [4];  [5];  [6];  [5];  [1]
+ Show Author Affiliations
  1. Boston College, Chestnut Hill, MA (United States). Dept. of Physics
  2. Harvard Univ., Cambridge, MA (United States). Dept. of Physics
  3. Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea
  4. National Inst. for Materials Science, Tsukuba (Japan)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  6. Seoul National Univ. (Korea, Republic of). Dept.of Physics and Astronomy
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1566819
Report Number(s):
BNL-212104-2019-JAAM
Journal ID: ISSN 1530-6984
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 19; Journal Issue: 8; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Higher order topology; 2D superconductor; hinge modes; Andreev reflection

Citation Formats

Gray, Mason J., Freudenstein, Josef, Zhao, Shu Yang F., O’Connor, Ryan, Jenkins, Samuel, Kumar, Narendra, Hoek, Marcel, Kopec, Abigail, Huh, Soonsang, Taniguchi, Takashi, Watanabe, Kenji, Zhong, Ruidan, Kim, Changyoung, Gu, G. D., and Burch, K. S. Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor. United States: N. p., 2019. Web. doi:10.1021/acs.nanolett.9b00844.
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Gray, Mason J., Freudenstein, Josef, Zhao, Shu Yang F., O’Connor, Ryan, Jenkins, Samuel, Kumar, Narendra, Hoek, Marcel, Kopec, Abigail, Huh, Soonsang, Taniguchi, Takashi, Watanabe, Kenji, Zhong, Ruidan, Kim, Changyoung, Gu, G. D., & Burch, K. S. Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor. United States. https://doi.org/10.1021/acs.nanolett.9b00844
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Gray, Mason J., Freudenstein, Josef, Zhao, Shu Yang F., O’Connor, Ryan, Jenkins, Samuel, Kumar, Narendra, Hoek, Marcel, Kopec, Abigail, Huh, Soonsang, Taniguchi, Takashi, Watanabe, Kenji, Zhong, Ruidan, Kim, Changyoung, Gu, G. D., and Burch, K. S. Wed . "Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor". United States. https://doi.org/10.1021/acs.nanolett.9b00844. https://www.osti.gov/servlets/purl/1566819.
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@article{osti_1566819,
title = {Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor},
author = {Gray, Mason J. and Freudenstein, Josef and Zhao, Shu Yang F. and O’Connor, Ryan and Jenkins, Samuel and Kumar, Narendra and Hoek, Marcel and Kopec, Abigail and Huh, Soonsang and Taniguchi, Takashi and Watanabe, Kenji and Zhong, Ruidan and Kim, Changyoung and Gu, G. D. and Burch, K. S.},
abstractNote = {Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s±, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the c-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.},
doi = {10.1021/acs.nanolett.9b00844},
journal = {Nano Letters},
number = 8,
volume = 19,
place = {United States},
year = {Wed Jul 03 00:00:00 EDT 2019},
month = {Wed Jul 03 00:00:00 EDT 2019}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1021/acs.nanolett.9b00844
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Cited by: 39 works
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Figures / Tables:

Figure 1 Figure 1: a) Theoretical band structure of FeTe0.55Se0.45 along the Γ-Z and (b) the X-Γ-M cuts. The pz orbital of the chalcogenide is shown in blue, crossing the three d-orbitals, resulting in two Dirac points and topological, spin-orbit gap. c) Resistance vs. Temperature graph for an exfoliated flake of FTS,more » showing a clear superconducting transition around 10K. d) Diagram showing the ingredients needed for a Helical Majorana Hinge Mode« less
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    Works referencing / citing this record:

    FeTe 0.55 Se 0.45 van der Waals tunneling devices
    journal, August 2019

    Superconductivity of Topological Surface States and Strong Proximity Effect in Sn 1–x Pb x Te‐Pb Heterostructures
    journal, September 2020

    Superconductivity of Topological Surface States and Strong Proximity Effect in Sn 1− x Pb x Te–Pb Heterostructures
    journal, November 2019

    Higher-Order Topological Odd-Parity Superconductors
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