Transport Study of the Proximity Effect of a Thin Superconducting Film on a Topological Insulator Bi_1.08Sn_0.02Sb_0.9Te₂S

A series of superconductor/topological insulator heterostructures was created by depositing a thin Pb layer on a surface of Bi_1.08Sn_0.02Sb_0.9Te₂S (BSSTS) flakes. The influence of the proximity effect on the transport properties of Pb/BSSTS heterostructures depending on the Pb layer thickness was studied. At thicknesses less than 20 nm, Pb forms separate regions on the BSSTS surface rather than a continuous layer. At a Pb layer thicknesses of up to 5 nm, no significant decrease in the superconducting transition temperature T_C of the Pb film on BSSTS is observed; it remains close to that of bulk Pb (7.2 K). Samples with a discontinuous thin Pb layer exhibit complex superconducting transition, which reflects superconducting correlations in the topological insulator surface layer.