Structure of the pairing gap from orbital nematic fluctuations

Tomoaki Agatsuma and Hiroyuki Yamase
Phys. Rev. B 94, 214505 – Published 9 December 2016

Abstract

We study superconducting instability from orbital nematic fluctuations in a minimal model consisting of the dxz and dyz orbitals, and choose model parameters which capture the typical Fermi surface geometry observed in iron-based superconductors. We solve the Eliashberg equations down to low temperatures with keeping the renormalization function and a full momentum dependence of the pairing gap. When superconductivity occurs in the tetragonal phase, we find that the pairing gap exhibits a weak momentum dependence over the Fermi surfaces. The superconducting instability occurs also inside the nematic phase. When the dxz orbital is occupied more than the dyz orbital in the nematic phase, a larger (smaller) gap is realized on the Fermi-surface parts where the dxz (dyz) orbital component is dominant, leading to a substantial momentum dependence of the pairing gap on the hole Fermi surfaces. On the other hand, the momentum dependence of the gap is weak on the electron Fermi surfaces. We also find that while the leading instability is the so-called s++-wave symmetry, the second leading one is dx2y2-wave symmetry. In particular, these two states are nearly degenerate in the tetragonal phase, whereas such quasidegeneracy is lifted in the nematic phase and the dx2y2-wave symmetry changes to highly anisotropic s-wave symmetry.

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  • Received 9 September 2016
  • Revised 7 November 2016

DOI:https://doi.org/10.1103/PhysRevB.94.214505

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Tomoaki Agatsuma and Hiroyuki Yamase

  • Department of Condensed Matter Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan and National Institute for Materials Science, Tsukuba 305-0047, Japan

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Issue

Vol. 94, Iss. 21 — 1 December 2016

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