  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.
