Peculiarities of diffusion thermopower with impurity electron topological transition in heavily doped bismuth wires

Abstract

This paper presents a series of investigations of differential thermopower and resistance in the temperature range of 4.2 – 300 K of samples shaped as glass-coated single-crystal Bi wires heavily doped with Sn acceptor impurity. An anomaly in the form of a triple sign change in the temperature dependences of thermopower α(Т) is detected. The effect is treated in terms of impurity electron topological transition (ETT), i.e. origination of Σ-band by doping bismuth wires with Sn acceptor impurity. The method of measuring Shubnikov-de-Haas oscillations in the main crystallographic directions in parallel (H I) and perpendicular (H I) directions was used to calculate the basic parameters of hole Fermi surfaces at points Т and L of the Brillouin zone, which made it possible to estimate the concentration and energy position of Σ -band in Bi and confirm that anomalies observed on traditional dependences of diffusion thermopower are specific features of ETT. The effect can be used for the discovery of ETT in the cases when research on the Fermi surface by oscillation methods is impossible, for instance, with heavy doping and in hightemperature region.