Strain-induced proximity effect in topological insulator TaSe$_3$

Abstract: The magnetoresistance of superconductor-topological insulator-superconductor structures, with indium as the superconductor and TaSe$_3$ as the topological insulator, shows steplike features on the resistance under magnetic fields. These resistance steps are resulted from the suppression of superconductivity, induced by the superconducting proximity effect in both the bulk and surface states of the topological insulator. The position and amplitude of the steps, occurring at approximately 0.1 T, show an unusual dependence on the magnitude of the uniaxial strain ($\epsilon$), indicating their connection with surface states. This behavior follows the expected transition sequence: semi-metal $\rightarrow$ strong topological insulator $\rightarrow$ trivial insulator, and supports the presence of surface states at $0.46\% \lesssim \epsilon \lesssim 0.85\%$.