Physical Properties of the Pb1-xSnxTe Solid Solutions in the Vicinity of the Topological Phase Transition

Abstract

Semiconductor Pb_1-xSn_xTe solid solutions (PSTS) are well known as promising materials widely used in the IR electronics, thermoelectricity and other fields of science and technology. Recently, it has been found that these alloys in certain concentration ranges exhibit the properties characteristic of the new quantum objects of solid-state physics – topological crystalline insulators (TCIs), whose unique properties define new possibilities for practical use of these materials in spintronics, quantum computing and thermoelectricity. The fact that in PSTS, the band inversion near some composition x_c leads to the emergence of the TCI states stimulates a detailed study of the behavior of the lattice, transport, and thermoelectric properties near x_c. The goal of the studies presented here was to reveal effects accompanying the band inversion in PSTS by measuring the x-dependences of the heat capacity C_p, microhardness H, lattice thermal conductivity \(\lambda\)_L electrical conductivity \(\sigma\), charge carrier mobility \(\mu\)_H, the Hall coefficient R_H, and the Seebeck coefficient S in the range x = (0.59 – 0.68), near the composition (x ~ 0.62) corresponding to the transition to an inversion  state at room temperature. It was established that the transition to the band inverted state is manifested through the appearance of peaks in the isotherms (T = 77-300 K) of  C_P, H, \(\sigma\), R_H , \(\mu\)_H, and S at x ~ 0.62. In the \(\lambda\)_L (X) isotherms, we observed two peaks near x =0.61 and x=0.63 and suggested that one peak corresponded to the band inversion point, and the other peak – to a structural self-organization process in the crystal lattice.