Pressure-induced superconductivity in non-stoichiometric bismuth telluride Bi35Te65

We performed x-ray diffraction study and electrical resistivity measurement of non-stoichiometric n-type Bi35Te65 under high pressure to investigate pressure-induced superconductivity and structural phase transition. Stoichiometric bismuth telluride (Bi2Te3), which is a p-type semiconductor, has the rhombohedral structure with space group R-3m at ambient condition. Pressure-induced superconductivity of stoichiometric p-type Bi2Te3 occurs in the high-pressure phases which appear above 8 GPa. Bi35Te65 has also the R-3m structure at ambient condition with electron carriers. X-ray diffraction study shows that the R-3m structure remains stable up to 8 GPa at room temperature. The superconducting transition in n-type Bi35Te65 is observed above 6 GPa; the transition temperature is 2.9 K at 6 GPa. The electrical resistivity at room temperature decreases rapidly at pressures from 7 to 8 GPa, indicating the occurrence of structural phase transition. It suggests that the superconducting transition at 6 GPa occurs at the ambient pressure phase with the R-3m structure.