Interfacially Enhanced Superconductivity in Fe(Te,Se)/BiTe Heterostructures.

Realizing topological superconductivity by integrating high-transition-temperature (T) superconductors with topological insulators can open new paths for quantum computing applications. Here, a new approach is reported for increasing the superconducting transition temperature by interfacing the unconventional superconductor Fe(Te,Se) with the topological insulator Bi-Te system in the low-Se doping regime, near where superconductivity vanishes in the bulk. The critical finding is that the of Fe(Te,Se) increases from nominally non-superconducting to as high as 12.5 K when BiTe is replaced with the topological phase BiTe. Interfacing Fe(Te,Se) with BiTe is also found to be critical for stabilizing superconductivity in monolayer films where can be as high as 6 K. Measurements of the electronic and crystalline structure of the BiTe layer reveal that a large electron transfer, epitaxial strain, and novel chemical reduction processes are critical factors for the enhancement of superconductivity. This novel route for enhancing T in an important epitaxial system provides new insight on the nature of interfacial superconductivity and a platform to identify and utilize new electronic phases.