Topological Surface States of Multicomponent Thermoelectrics Based on Bismuth Telluride

Abstract

The surface states of Dirac fermions in p-Bi₂Te₃, p-Bi_{2 –x}Sb_xTe_{3 –y}Se_y, and p-Bi_{2 –x–y}Sn_xGe_yTe₃ thermoelectrics were studied and its topological characteristics were obtained by scanning tunneling techniques in dependence on compositions. It was shown that the thermoelectric power factor and the material parameter enhance with the shift of the Dirac point to the top of the valence band with the increasing of atomic substitution in these thermoelectrics. A growth contribution of the surface states is determined by an increase of the Fermi velocity for large atomic substitutions of Bi at x > 1.5 and small substitutions in the Te sublattice (y = 0.06). In compositions with smaller substitutions at x = 1–1.3 and y = 0.06–0.09, similar effect of the surface states is determined due to raising the surface concentration of charge carriers.