Kharkhalis L. Localized and delocalized states and effects of interparticle interactions in low-symmetry semiconducting crystals

The thesis presents results of the complex investigations of the fundamental characteristics for the low-symmetry semiconductors with using the modern methods of band structure calculations and group-theoretical methods. A nonstandart dispersion law with a low-energy non-parabolicity for charge carriers has been obtained for the layered In4Se3 crystal. The consequences of non-parabolicity of dispersion law are studied for physical parameters and manifestation of new effects in strogly anisotropic crystals (peak-like density of states which leads to the strong electron-phonon interaction and the creation of the charge inhomogeneity (condenson states), the anomaly of fundamental absorption edge in In4Se3; the anomalous anisotropy of the effective masses in the layered InSe crystal; the realization of plasma-electric effect in In4Se3). It has been investigated the influences of the intercalated impurities and the shear strains on the energy structure of the layered crystal. The fundamental investigations on the formation of new functional low-symmetry materials with the controlled physical parameters were carried out (the solid solutions of Cd0.5Zn0.5Sb and the Hg3TeCl4 crystal).