Epitaxial growth of superconducting FeTe1-xSex film on a topological insulator*

Integrating a superconductor (SC) and a topological insulator (TI) in a heterostructure via proximity effect is a promising approach for realizing topological superconductor. In particular, superconducting Fe(Te,Se) is one of the best candidates to create such a heterostructure with chalcogenide TIs. Nonetheless, stringent lattice-matching requirement of the Fe(Te,Se) films does not allow four-fold Fe(Te,Se) layer to grow properly on six-fold TI platform, although TI films can grow well on Fe(Te,Se) via van der Waals epitaxy. Here, surprisingly we discover that Fe(Te,Se) can grow epitaxially on a TI (Bi2Te3) layer with Tc as high as 13 K. Furthermore, this is the very first TI-SC heterostructure platform that can be formed in either of TI-on-SC or SC-on-TI sequence, opening a route to unprecedented topological heterostructures such as Weyl superconductors.