Electronic Structure and Transport Properties of Bi₂Te₃ and Bi₂Se₃ Single Crystals

The electrical resistivity and the Hall effect of topological insulator Bi₂Te₃ and Bi₂Se₃ single crystals were studied in the temperature range from 4.2 to 300 K and in magnetic fields up to 10 T. Theoretical calculations of the electronic structure of these compounds were carried out in density functional approach, taking into account spin-orbit coupling and crystal structure data for temperatures of 5, 50 and 300 K. A clear correlation was found between the density of electronic states at the Fermi level and the current carrier concentration. In the case of Bi₂Te₃, the density of states at the Fermi level and the current carrier concentration increase with increasing temperature, from 0.296 states eV^-1 cell^-1 (5 K) to 0.307 states eV^-1 cell^-1 (300 K) and from 0.9 × 10¹⁹ cm^-3 (5 K) to 2.6 × 10¹⁹ cm^-3 (300 K), respectively. On the contrary, in the case of Bi₂Se₃, the density of states decreases with increasing temperature, from 0.201 states eV^-1 cell^-1 (5 K) to 0.198 states eV^-1 cell^-1 (300 K), and, as a consequence, the charge carrier concentration also decreases from 2.94 × 10¹⁹ cm^-3 (5 K) to 2.81 × 10¹⁹ cm^-3 (300 K).