Band Jahn–Teller distortion and superconducting excitations in Raman spectra

We report the calculation of the phonon response of the coexistent band Jahn–Teller distortion and the superconducting (SC) state and predict the possibility of the observation of the SC and the lattice distortion gap excitations in the Raman spectra of some of the high-temperature superconductors. A theoretical model study is made for the coexistent phase in the presence of electron–phonon (EP) interaction. The scattering due to the charge carriers proceeds through their coupling to the phonon resulting in the renormalisation of the later. The phonon Green’s function is calculated by Zubarev’s technique and the phonon self-energy due to the EP interaction which is given by the electron density response function in the coexistent phase is calculated. The phonon spectral density therefore predicts the Raman intensities of the system in the presence of the coexistence of the structural transition and the s-wave BCS superconductivity.