Rezumat
CZU 539.261.1
This paper reports results of an experimental study of electronic topological transitions in bismuth wires in a glass cover doped with acceptor (Sn) and donor (Te) impurities. Measurements of the temperature dependence of the thermoelectric power and resistance were carried out in the temperature range 1.5–300K and magnetic fields up to 14T. The position of the Fermi level eF and the concentration of charge carriers at doping were estimated from the Shubnikov de Haas (SdH) oscillations which were clearly visible, from both L-electrons, L and T-holes in all crystallographic directions. We demonstrate anomalies in the temperature dependences of the thermopower in Bi wires doped by acceptor (Sn) and donor (Te) impurities in the form of a triple (doping Sn) and double (doping Te) change in the sign of the thermopower. The effect is interpreted in terms of the manifestation of impurity Lifshitz topological transitions. SdH oscillations method has been used to determine the energy position of the Σ-band by doping Bi wires with the acceptor impurity Sn and T bands conduction at doping with Te. It is shown that the appearance of the Σ and T bands in Bi wires doped by the acceptor and donor impurities is responsible for the singularity in the thermo-electric powder, which is in reasonable agreement with theoretical models and predictions.
Keywords: electronic topological transitions, thermopower, Shubnikov de Haas oscillations, Bi wires impurities.