Collective modes in multiband superconductors: Raman scattering in iron selenides

M. Khodas, A. V. Chubukov, G. Blumberg

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24 Scopus citations

Abstract

We study Raman scattering in the superconducting state of alkali-intercalated iron selenide materials AxFe2-ySe2 (A=K,Rb,Cs) in which the Fermi surface has only electron pockets. Theory predicts that both s-wave and d-wave pairing channels are attractive in this material, and the gap can have either s-wave or d-wave symmetry, depending on the system parameters. ARPES data favor s-wave superconductivity. We present the theory of Raman scattering in AxFe2-ySe2 assuming that the ground state has s-wave symmetry but d wave is a close second. We argue that Raman profile in d-wave B2g channel displays two collective modes. One is a particle-hole exciton, another is a Bardasis-Schrieffer-type mode associated with superconducting fluctuations in d-wave channel. At a finite damping, the two modes merge into one broad peak. We present Raman data for AxFe2-ySe2 and compare them with theoretical Raman profile.

Original languageEnglish (US)
Article number245134
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume89
Issue number24
DOIs
StatePublished - Jun 26 2014
Externally publishedYes

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