Pressure-Induced Electronic Topological Transition and Superconductivity in Topological Insulator Bi₂Te_2.1Se_0.9

One approach to discovering topological superconductors is establishing superconductivity based on well-identified topological insulators. However, the coexistence of superconductivity and a topological state is always arcane. In this paper, we report how pressure tunes the crystal structure, electronic structure, and superconductivity in topological insulator Bi₂Te_2.1Se_0.9. At ∼2.5 GPa, the abnormal changes in c/a and the full width at half-maximum of the A_1g¹ mode indicate the occurrence of an electronic topological transition. The pressure-induced superconductivity in Bi₂Te_2.1Se_0.9 pinned with an electronic topological transition presents at 2.4 GPa, which is far below the structural phase transition pressure of 8.4 GPa. These results suggest that the appearance of an electronic topological transition is closely correlated with superconductivity in the initial phase, where the topological surface state persists. Our work clarifies the complex electronic structure of Bi₂Te_2.1Se_0.9 and sheds light on the mechanism for superconductivity in topological insulators.