LAUSR

Superconducting proximity effect (SPE) induces superconductivity transition in the otherwise non superconducting thin-film in proximity with a superconductor. The SPE usually occurs in real space and decays exponentially with the film thickness. Herein, we unveiled an abnormal SPE in a topological insulator (TI)/superconductor heterostructure, which is attributed to the topologically protected surface state. Surprisingly, such abnormal SPE occurs in momentum space regardless the TI film thickness, as long as the topological surface states are robust and form a continuous conduction loop. Combining transport measurements and scanning tunneling microscopy/spectroscopy techniques, we explored the SPE in Bi2 Se3 /FeSe0.5 Te0.5 heterostructures, where Bi2 Se3 is an ideal three-dimensional topological insulator and FeSe0.5 Te0.5 a typical iron-based superconductor. As the thickness of the Bi2 Se3 thin-film exceeds 400 nanometers, there still exits SPE-induced superconductivity on the surface of Bi2 Se3 thin-film with a transition temperature Tc not less than 10 K. Such an extraordinary behavior is induced by the unique properties of topologically protected surface states of Bi2 Se3 . This research will deepen the understanding of important role of topologically protected surface states in the SPE. This article is protected by copyright. All rights reserved.