The phonon-induced line shape of the dynamical Stark effect in Cu2O

Abstract
The authors study the influence of electron-phonon coupling on the resonant dynamical Stark effect in Cu2O. They start from a multi-band density matrix theory involving directly forbidden dipole transitions and directly allowed quadrupole transitions. The use of the multi-band formalism is necessary for the inclusion of the observed polarization effects. From a microscopic treatment of the electron-phonon interaction they derive a frequency-dependent transverse relaxation for the excitons and a renormalization of the optical transition matrix elements resulting in a Fano effect. They derive an expression for the differential transmission, taking into account a parametric sum frequency generation. Theoretical and experimental data are compared, showing satisfactory agreement.