Topological superconductivity is an exotic state of matter that supports Majorana zero-modes, which have been predicted to occur in the surface states of three-dimensional systems. Recently the foreseeing was experimentally observed in the topological insulator Sb₂Te₃ with an emergent surface superconductivity [1]. The surface superconductivity on top and bottom surfaces of a bulk are individual and irrelevant, however as the thickness of a bulk reduces to a nanometer range, the top and bottom surfaces approach to each other, they should become an integral part of the whole system. To demonstrate the idea, nanoflakes of single crystal Sb₂Te₃ with various thickness d were grown. Experimental data and theoretical analyses show that the superconductivity in Sb₂Te₃ nanoflakes for d < 9 nm a new class of superconductivity origins from pairing between top and bottom surfaces Dirac fermions. The funding of emergent inter-surface superconductivity dominated by the spinful pairing in specimens below 9 nm illuminate a new path to the study of topological superconductivity.
[1] Zhao, L; Deng, H; Korzhovska, I; Begliarbekov, M; Chen, Zh; Andrade, E; Rosenthal, E; Pasupathy, A; Oganesyan, V; Krusin-Elbaum, L. Nat .Commun. 2015, 6, 8279, 2015