Band edge motion in quantizing magnetic field and nonequilibrium states in Pb_1−x Sn _x Te alloys doped with In

Abstract

Galvanomagnetic and oscillation effects in Pb_1−x Sn _x Te single crystals doped with 0.5 at % In have been studied in magnetic fields up to 60 kOe at temperatures from 4.2 to 30 K under hydrostatic pressure up to 18 kbar. Beyond the ultraquantum magnetic field limit (H _uql) for the metallic state of Pb_1−x Sn _x Te(In) alloys, Fermi level pinning by high-density quasilocal states takes place. In a strong fieldH>H _uql the equationE _F = const is valid instead of the equationn = const which is usual for degenerate semiconductors (E _F is the electron or hole Fermi energy, andn is their concentration). This makes it possible to determine the direction of the band edge motion in the Pb_1−x Sn _x Te energy spectrum in a quantizing magnetic field in the direct and inverse spectral regions. It is found that the charge carrier transitions between quasilocal and band states are of anomalously long duration (∼10⁵ sec atT=4.2 K). By the application of a quantizing magnetic field we obtained a nonequilibrium metallic state of the system with a frozen or slowly diminishing Fermi surface. The characteristic time of the transition was found as a function of temperature and pressure. The relaxation kinetics of the nonequilibrium states induced by a quantizing magnetic field and infrared irradiation is discussed.