Investigation of valence band structures in p-type Pbsub(1-x)Snsub(x)Te in the neighbourhood of phase transition

Results of experimental investigation into the temperature dependence of band parameters, lattice permittivity and concentration of light and heavy holes in p-type Pbsub(1-x)Snsub(x)Te, using magnetoplasma waves, are presented. On the temperature curve of the lattice permittivity and band parameters at T0=20 K their values become extreme, which is related to the structural phase transition. The phase transition is shown to cause the band spectrum reconstruction accompanied by a reduction in the energy gap between the upper limits of valence bands of light and heavy holes, localized in the L- and Σ-points of a Brillouin zones, respectively, and by a change in the form of the constant energy surface of these holes