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Title: Coulomb problem in iron-based superconductors

Abstract

We discuss the role of strong Coulomb interactions in iron-based superconductors (FeSCs). The presumed s± character of these superconductors means that the condensate is not symmetry protected against Coulomb repulsion. Remarkably, the transition temperatures and the excitation gap are quite robust across the large family of iron-based superconductors, despite drastic changes in Fermi-surface geometry. Here, the Coulomb problem is to understand how these superconductors avoid the strong on-site Coulomb interaction of the iron atoms, while maintaining a robust transition temperature. Within the dominant space of t2g orbitals, on-site repulsion in the FeSCs forces two linearly independent components of the condensate to vanish. This raises the possibility that iron-based superconductors might adapt their condensate to the Coulomb constraints by rotating the pairing state within the large manifold of entangled extended s-wave gap functions with different orbital and momentum space structure. We examine this “orbital and k-space flexibility” (OKF) mechanism using both Landau theory and microscopic calculations within a multiorbital t-J model. Based on our results, we conclude that OKF necessitates a large condensate degeneracy. One interesting possibility raised by our results is that a resolution to the Coulomb problem in FeSCs might require a reconsideration of triplet pairing.

Authors:
ORCiD logo [1]; ORCiD logo [2]
  1. Rutgers Univ., Piscataway, NJ (United States)
  2. Rutgers Univ., Piscataway, NJ (United States); Univ. of London, Egham (United Kingdom)
Publication Date:
Research Org.:
Rutgers Univ., Piscataway, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1509641
Alternate Identifier(s):
OSTI ID: 1509513
Grant/Contract Number:  
FG02-99ER45790
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 99; Journal Issue: 14; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Iron based superconductivity; Unconventional superconductivity

Citation Formats

König, Elio J., and Coleman, Piers. Coulomb problem in iron-based superconductors. United States: N. p., 2019. Web. doi:10.1103/PhysRevB.99.144522.
König, Elio J., & Coleman, Piers. Coulomb problem in iron-based superconductors. United States. doi:10.1103/PhysRevB.99.144522.
König, Elio J., and Coleman, Piers. Fri . "Coulomb problem in iron-based superconductors". United States. doi:10.1103/PhysRevB.99.144522. https://www.osti.gov/servlets/purl/1509641.
@article{osti_1509641,
title = {Coulomb problem in iron-based superconductors},
author = {König, Elio J. and Coleman, Piers},
abstractNote = {We discuss the role of strong Coulomb interactions in iron-based superconductors (FeSCs). The presumed s± character of these superconductors means that the condensate is not symmetry protected against Coulomb repulsion. Remarkably, the transition temperatures and the excitation gap are quite robust across the large family of iron-based superconductors, despite drastic changes in Fermi-surface geometry. Here, the Coulomb problem is to understand how these superconductors avoid the strong on-site Coulomb interaction of the iron atoms, while maintaining a robust transition temperature. Within the dominant space of t2g orbitals, on-site repulsion in the FeSCs forces two linearly independent components of the condensate to vanish. This raises the possibility that iron-based superconductors might adapt their condensate to the Coulomb constraints by rotating the pairing state within the large manifold of entangled extended s-wave gap functions with different orbital and momentum space structure. We examine this “orbital and k-space flexibility” (OKF) mechanism using both Landau theory and microscopic calculations within a multiorbital t-J model. Based on our results, we conclude that OKF necessitates a large condensate degeneracy. One interesting possibility raised by our results is that a resolution to the Coulomb problem in FeSCs might require a reconsideration of triplet pairing.},
doi = {10.1103/PhysRevB.99.144522},
journal = {Physical Review B},
number = 14,
volume = 99,
place = {United States},
year = {2019},
month = {4}
}

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