Coexistence of isotropic and extended s-wave order parameters in FeSe as revealed by low-temperature specific heat

Jiunn-Yuan Lin*, Y. S. Hsieh, D. A. Chareev, A. N. Vasiliev, Y. Parsons, H. D. Yang

*Corresponding author for this work

Research output: Contribution to journalArticle

101 Scopus citations

Abstract

The comprehensive low-temperature specific-heat C(T) data identify both an isotropic s-wave and extended s-wave order parameters coexisting in a superconducting single-crystal FeSe with T c = 8.11 K. The isotropic gap Δ 0 = 1.33 meV on the hole Fermi sheets and the extended s-wave gap Δ = Δ e(1+αcos2) with Δ e = 1.13 meV and α = 0.78 on the electron Fermi sheets. The extended s wave is rather anisotropic, but the low-energy quasiparticle excitations demonstrate no sign of the accidental nodes. The coefficient γ(H) manifesting the quasiparticle contribution to C is a nonlinear function of the applied magnetic field H in the mixed state in accord with the anisotropic multiorder parameters.

Original languageEnglish
Article number220507
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number22
DOIs
StatePublished - 27 Dec 2011

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