Raman signatures of pressure induced electronic topological and structural transitions in Bi2Te3

We report Raman signatures of electronic topological transition (ETT) at 3.6 GPa and rhombohedral ( α - Bi2Te3) to monoclinic ( β - Bi2Te3) structural transition at ∼8 GPa. At the onset of ETT, a new Raman mode appears near 107 cm−1 which is dispersionless with pressure. The structural transition at ∼8 GPa is marked by a change in pressure derivative of A1g and Eg mode frequencies as well as by appearance of new modes near 115 cm−1 and 135 cm−1. The mode Grüneisen parameters are determined in both the α and β -phases.