Realization of topological superconductors (TSCs) hosting Majorana fermions is a central challenge in condensed-matter physics. One approach is to use the superconducting proximity effect (SPE) in heterostructures, where a topological insulator contacted with a superconductor hosts an effective p-wave pairing by the penetration of Cooper pairs across the interface. However, this approach suffers a difficulty in accessing the topological interface buried deep beneath the surface. Here, we propose an alternative approach to realize topological superconductivity without SPE. In a Pb(111) thin film grown on TlBiSe2, we discover that the Dirac-cone state of substrate TlBiSe2 migrates to the top surface of Pb film and obtains an energy gap below the superconducting transition temperature of Pb. This suggests that a BCS superconductor is converted into a TSC by the topological proximity effect. Our discovery opens a route to manipulate topological superconducting properties of materials.
@article{arxiv.2003.04562,
title = {Conversion of a conventional superconductor into a topological superconductor by topological proximity effect},
author = {C. X. Trang and N. Shimamura and K. Nakayama and S. Souma and K. Sugawara and I. Watanabe and K. Yamauchi and T. Oguchi and K. Segawa and T. Takahashi and Yoichi Ando and T. Sato},
journal= {arXiv preprint arXiv:2003.04562},
year = {2020}
}