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

Leong, Zhidong; Phillips, Philip

doi:10.1103/PhysRevB.93.155159

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

Journal Article · Wed Apr 27 00:00:00 EDT 2016 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.93.155159· OSTI ID:1387865

Leong, Zhidong ^[1]; Phillips, Philip ^[1]

Univ. of Illinois at Urbana-Champaign, IL (United States)

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 T_c 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.

View Accepted Manuscript (DOE)

Research Organization:: Energy Frontier Research Centers (EFRC) (United States). Center for Emergent Superconductivity (CES)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)

Grant/Contract Number:: AC02-98CH10886

OSTI ID:: 1387865

Alternate ID(s):: OSTI ID: 1249945

Journal Information:: Physical Review B, Journal Name: Physical Review B Journal Issue: 15 Vol. 93; ISSN 2469-9950; ISSN PRBMDO

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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