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Title: Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers

Superconductivity that spontaneously breaks time-reversal symmetry (TRS) has been found, so far, only in a handful of three-dimensional (3D) crystals with bulk inversion symmetry. We report an observation of spontaneous TRS breaking in a 2D superconducting system without inversion symmetry: the epitaxial bilayer films of bismuth and nickel. The evidence comes from the onset of the polar Kerr effect at the superconducting transition in the absence of an external magnetic field, detected by the ultrasensitive loop-less fiber-optic Sagnac interferometer. Because of strong spin-orbit interaction and lack of inversion symmetry in a Bi/Ni bilayer, superconducting pairing cannot be classified as singlet or triplet.We propose a theoretical model where magnetic fluctuations in Ni induce the superconducting pairing of the d xy ± id x2-y2 orbital symmetry between the electrons in Bi. In this model, the order parameter spontaneously breaks the TRS and has a nonzero phase winding number around the Fermi surface, thus making it a rare example of a 2D topological superconductor.
Authors:
 [1] ;  [2] ;  [3] ; ORCiD logo [4] ;  [4] ;  [4] ;  [2] ;  [2] ;  [3]
  1. Univ. of California, Irvine, CA (United States). Department of Physics and Astronomy; Fudan Univ., Shanghai (China). Department of Physics
  2. Univ. of Maryland, College Park, MD (United States). Department of Physics, Condensed Matter Theory Center and Joint Quantum Institute
  3. Univ. of California, Irvine, CA (United States). Department of Physics and Astronomy
  4. Fudan Univ., Shanghai (China). Department of Physics
Publication Date:
Grant/Contract Number:
SC0001911
Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 3; Journal Issue: 3; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Research Org:
Univ. of Maryland, College Park, MD (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1424726

Gong, Xinxin, Kargarian, Mehdi, Stern, Alex, Yue, Di, Zhou, Hexin, Jin, Xiaofeng, Galitski, Victor M., Yakovenko, Victor M., and Xia, Jing. Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers. United States: N. p., Web. doi:10.1126/sciadv.1602579.
Gong, Xinxin, Kargarian, Mehdi, Stern, Alex, Yue, Di, Zhou, Hexin, Jin, Xiaofeng, Galitski, Victor M., Yakovenko, Victor M., & Xia, Jing. Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers. United States. doi:10.1126/sciadv.1602579.
Gong, Xinxin, Kargarian, Mehdi, Stern, Alex, Yue, Di, Zhou, Hexin, Jin, Xiaofeng, Galitski, Victor M., Yakovenko, Victor M., and Xia, Jing. 2017. "Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers". United States. doi:10.1126/sciadv.1602579. https://www.osti.gov/servlets/purl/1424726.
@article{osti_1424726,
title = {Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers},
author = {Gong, Xinxin and Kargarian, Mehdi and Stern, Alex and Yue, Di and Zhou, Hexin and Jin, Xiaofeng and Galitski, Victor M. and Yakovenko, Victor M. and Xia, Jing},
abstractNote = {Superconductivity that spontaneously breaks time-reversal symmetry (TRS) has been found, so far, only in a handful of three-dimensional (3D) crystals with bulk inversion symmetry. We report an observation of spontaneous TRS breaking in a 2D superconducting system without inversion symmetry: the epitaxial bilayer films of bismuth and nickel. The evidence comes from the onset of the polar Kerr effect at the superconducting transition in the absence of an external magnetic field, detected by the ultrasensitive loop-less fiber-optic Sagnac interferometer. Because of strong spin-orbit interaction and lack of inversion symmetry in a Bi/Ni bilayer, superconducting pairing cannot be classified as singlet or triplet.We propose a theoretical model where magnetic fluctuations in Ni induce the superconducting pairing of the dxy ± idx2-y2 orbital symmetry between the electrons in Bi. In this model, the order parameter spontaneously breaks the TRS and has a nonzero phase winding number around the Fermi surface, thus making it a rare example of a 2D topological superconductor.},
doi = {10.1126/sciadv.1602579},
journal = {Science Advances},
number = 3,
volume = 3,
place = {United States},
year = {2017},
month = {3}
}

Works referenced in this record:

Role of Spin in Quasiparticle Interference
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  • Physical Review Letters, Vol. 93, Issue 19, Article No. 196802
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