Single Crystals*

We have investigated the magneto-transport properties of topological single crystals, Sb₂Te_2-xSe_x. The electrical resistance decreases with temperature showing a metallic behavior. Under high magnetic fields, magnetoresistance (MR) increases almost linearly with the applied field, and it reaches a value as high as 300 % at 14 T with no sign of saturation. In addition, the MR shows clear Shubnikov de Haas (SdH) oscillations with a single frequency. To explore the Fermi surface topology, we have carried out detailed angle dependence measurements of SdH oscillations and determined the Berry phase characteristics. We have also analyzed the temperature-dependent quantum oscillations using the Lifshitz-Kosevich theory and calculated several physical parameters characterizing the SdH oscillations.