Collective modes in multiband superconductors: Raman scattering in iron selenides

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

doi:10.1103/PhysRevB.89.245134

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Collective modes in multiband superconductors: Raman scattering in iron selenides

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

DOI 10.1103/PhysRevB.89.245134 · Physical Review B

T1

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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.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
K0.75Fe1.75Se2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
K0.75Fe1.75Se2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown