Two-band model of Raman scattering on iron pnictide superconductors

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Based on a two-band model, we study the electronic Raman scattering intensity in both normal and superconducting states of iron-pnictide superconductors. For the normal state, due to the match or mismatch of the symmetries between band hybridization and Raman vertex, it is predicted that overall B₁g Raman intensity should be much weaker than that of the B₂g channel. Moreover, in the non-resonant regime, there should exhibit a interband excitation peak at frequency ω≃ 7.3 t₁ (6.8t₁) in the B₁g (B₂g) channel. For the superconducting state, it is shown that β-band contributes most to the B₂g Raman intensity as a result of multiple effects of Raman vertex, gap symmetry, and Fermi surface topology. Both extended s- and dxy-wave pairings in the unfolded BZ can give a good description to the reported B₂g Raman data [Muschler et al., Phys. Rev. B. 80, 180510 (2009).], while dₓ₂₋y₂-wave pairing in the unfolded BZ seems to be ruled out.