Topological Surface States of Dirac Fermions in n-Bi2Te3 –ySey Thermoelectrics

Abstract

In n-Bi₂Te₃ and n-Bi₂Te_{3 –y}Se_y thermoelectrics, the surface states of Dirac fermions of the interlayer Van der Waals surface (0001) are studied by scanning tunneling microscopy and spectroscopy. The surface morphology and modulated line profiles of the tunneling microscopy images are determined by local distortions of the surface density of electronic states and depend on the composition. The Dirac point E_D in the studied compositions is localized in the band gap and shifts to the top of the valence band with increasing Se content in n-Bi₂Te_{3 –y}Se_y alloys. The dependence between the parameters of the surface states of Dirac fermions (Dirac-point position, Fermi velocity, surface fermion concentration) and thermoelectric properties (Seebeck coefficient and power parameter) in the thermoelectrics under study is determined.