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 ({\alpha}-Bi2Te3) to monoclinic ({\beta}-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-1and 135 cm-1. The mode Gr\"uneisen parameters are determined in both the {\alpha} and {\beta}-phases. 
Gopal K. Pradhan, Achintya Bera, Pradeep Kumar, D. V. S. Muthu and A.   K. Sood
cond-mat.mtrl-sci cond-mat.other