Electron transitions in strong magnetic fields

Abstract

Various types of electron transitions in strong magnetic fields due to qualitative changes of the energy spectrum of electrons (and hence of properties of materials) were predicted and observed at certain critical values of the magnetic field. Metallic and semiconducting Bi-Sb alloys were investigated in the concentration range of Sb up to 8 at % and from 8 at % to 16 at % correspondingly. The transversal and longitudinal magnetoresistance measurements on Bi-Sb alloy single crystals were performed at various orientations of current and fields relative to the crystalline axes. The measurements were performed in magnetic fields up to 600 kOe.at temperatures from 4.2 to 77°K. The following types of electron transitions were discovered: (a) semiconductor-metal transition; (b) a transition from a semiconducting state into a state with an abnormally small energy gap between the zones referred to as a “quasimetallic”; (c) a transition semiconductor-“quasimetal”-semiconductor; (d) a transition semiconductor-“quasimetal”-semiconductor-metal; and (e) metal-semiconductor transition.