Interfacially enhanced superconductivity in Fe(Te,Se)/Bi 4 Te 3 heterostructures.

Realizing topological superconductivity by integrating high-transition-temperature (T C ) superconductors with topological insulators can open new paths for quantum computing applications. Here, we report a new approach for increasing the superconducting transition temperature ( T C o n s e t ) $( {T_C^{onset}} )$ 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 T C o n s e t $T_C^{onset}$ of Fe(Te,Se) increases from nominally non-superconducting to as high as 12.5 K when Bi 2 Te 3 is replaced with the topological phase Bi 4 Te 3 . Interfacing Fe(Te,Se) with Bi 4 Te 3 is also found to be critical for stabilizing superconductivity in monolayer films where T C o n s e t $T_C^{onset}$ can be as high as 6 K. Measurements of the electronic and crystalline structure of the Bi 4 Te 3 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 C in an important epitaxial system provides new insight on the nature of interfacial superconductivity and a platform to identify and utilize new electronic phases. This article is protected by copyright. All rights reserved.