Multiphonon renormalization of the spectrum of two-dimensional excitons in a magnetic field

The renormalization of the dispersion law for two-dimensional excitons in a magnetic field is studied by the Green's-function method taking into account multiphonon processes. Since a magnetic field alters the internal state of an exciton, this changes the binding force between quasiparticles and phonons, intensifying or weakening it depending on the parameters of the crystals. The authors therefore study the renormalization of the quasiparticle spectrum by optical phonons without assuming that the interaction is weak in the sense of perturbation theory