Plasmon-phonon-polaron in bismuth-antimony alloys doped with an acceptor impurity

Phonon spectra of bismuth crystals and bismuth-antimony alloys give evidence of the existence of phonon-polarons caused by valent electrons polarization which results in softening of the transverse mode and hardening of the longitudinal mode of optical vibrations of the crystal lattice. Doping of bismuth-antimony alloys by acceptor tin addition results in drawing together of the plasma oscillation energy of free charge carriers and the energy of longitudinal optical phonons. In this case the behavior of the dielectric function is described within the framework of the model corresponding to plasmon-phonon-polaron excitation