Optical spectra of strong-coupling polarons

The photodissociation spectra of Landau-Pekar polarons are calculated using the theory of quantum coherent states. It is shown that the number of phonons emitted in one dissociation event can differ and that their energy is equal to the doubled polaron binding energy Ep only on the average. It is established that the absorption spectrum is a superposition of bands corresponding to different numbers of phonons emitted during the dissociation of one polaron and that the half-width of each of the bands is much greater than the distance between the bands (which is equal to the phonon energy ℏθ). Therefore, the absorption spectrum looks like a very wide unstructured band with the low-frequency edge lying at Ep + ℏθ, a maximum at an energy of about 5Ep (for the band carrier mass equal to (1–3)me), and the half-width being of the order of the energy corresponding to the maximum.