Collective modes in multiband superconductors: Raman scattering in iron selenides

Abstract

We study Raman scattering in the superconducting state of alkali-intercalated iron selenide materials AxFe2-ySe2 (A=K,Rb,Cs) in which 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.

16 pages, 7 figures

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Cited by in corpus (13)

• Hund interaction, spin-orbit coupling and the mechanism of superconductivity in strongly hole-doped iron pnictides
• Manipulation of gap nodes by uniaxial strain in iron-based superconductors
• Probing the pairing interaction and multiple Bardasis-Schrieffer modes using Raman spectroscopy
• Superconductivity and electronic fluctuations in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ studied by Raman scattering
• Optical response of the Leggett mode in multiband superconductors in the linear response regime
• Displacement and annihilation of Dirac gap-nodes in d-wave iron-based superconductors
• Raman Study of Cooper Pairing Instabilities in (Li${}_{1-x}$Fe${}_x$)OHFeSe
• Many-body physics-induced selection rules: application to Raman spectroscopy
• Doping evolution of the gap structure and spin-fluctuation pairing in $Ba(F{e}_{1-x}C{o}_x{)}_{2}A{s}_2$ superconductors
• Electronic Raman response of a superconductor across a time reversal symmetry breaking phase transition
• Effect of pairing fluctuations on the spin resonance in Fe-based superconductors
• Raman response of collective modes in multicomponent superconductors
• Universal nonanalytic features in response functions of anisotropic superconductors