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Title: Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors

Abstract

Recent angle-resolved photoemission spectroscopy measurements of Co-doped LiFeAs report a large and robust superconducting gap on the Γ-centered hole band that lies 8 meV below the Fermi level. We show that, unlike a conventional superconductor described by BCS theory, a multiband system with strong interband Coulomb interactions can explain these observations. We model LiFeAs with a five-band model in which the shallow hole band is coupled with the other bands by only Coulomb interactions. Using Eliashberg theory, we find reasonable interaction parameters that reproduce the Tc and all five gaps of LiFeAs. The energy independence of the Coulomb interactions then ensures the robustness of the gap induced on the shallow band. Furthermore, due to the repulsive nature of the Coulomb interactions, the gap changes sign between the shallow band and the other hole pockets, corresponding to an unconventional s± gap symmetry. Unlike other families of iron-based superconductors, the gap symmetry of LiFeAs has not been ascertained experimentally. Finally, the experimental implications of this sign-changing state are discussed.

Authors:
 [1];  [1]
  1. Univ. of Illinois at Urbana-Champaign, IL (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Emergent Superconductivity (CES)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1387865
Alternate Identifier(s):
OSTI ID: 1249945
Grant/Contract Number:  
AC02-98CH10886
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 15; Related Information: CES partners with Brookhaven National Laboratory (BNL); Argonne National Laboratory; University of Illinois, Urbana-Champaign; Los Alamos National Laboratory; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; phonons; thermal conductivity; energy storage (including batteries and capacitors); superconductivity; defects; spin dynamics

Citation Formats

Leong, Zhidong, and Phillips, Philip. Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors. United States: N. p., 2016. Web. doi:10.1103/PhysRevB.93.155159.
Leong, Zhidong, & Phillips, Philip. Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors. United States. doi:10.1103/PhysRevB.93.155159.
Leong, Zhidong, and Phillips, Philip. Wed . "Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors". United States. doi:10.1103/PhysRevB.93.155159. https://www.osti.gov/servlets/purl/1387865.
@article{osti_1387865,
title = {Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors},
author = {Leong, Zhidong and Phillips, Philip},
abstractNote = {Recent angle-resolved photoemission spectroscopy measurements of Co-doped LiFeAs report a large and robust superconducting gap on the Γ-centered hole band that lies 8 meV below the Fermi level. We show that, unlike a conventional superconductor described by BCS theory, a multiband system with strong interband Coulomb interactions can explain these observations. We model LiFeAs with a five-band model in which the shallow hole band is coupled with the other bands by only Coulomb interactions. Using Eliashberg theory, we find reasonable interaction parameters that reproduce the Tc and all five gaps of LiFeAs. The energy independence of the Coulomb interactions then ensures the robustness of the gap induced on the shallow band. Furthermore, due to the repulsive nature of the Coulomb interactions, the gap changes sign between the shallow band and the other hole pockets, corresponding to an unconventional s± gap symmetry. Unlike other families of iron-based superconductors, the gap symmetry of LiFeAs has not been ascertained experimentally. Finally, the experimental implications of this sign-changing state are discussed.},
doi = {10.1103/PhysRevB.93.155159},
journal = {Physical Review B},
number = 15,
volume = 93,
place = {United States},
year = {2016},
month = {4}
}

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