A New Route to Topological Superconductivity: Superconductivity of Inter-Surface Pairing in Topological Insulators
Chung-Yu Mou1*, Yang-Yuan Chen2, Min-Nan Ou2, Sergey R. Harutyunyan3, Ting-Kuo Lee2, W.H. Tsai2, F.Y. Chiu2, Po-Hao Chou1, C.H. Chien2, P.C. Lee2, Y.C. Chang2
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Institute of Physics, Academia Sinica, Nankang, Taiwan
3Institute for Physical Research, NASRA, Ashtarak,, Armenia
* Presenter:Chung-Yu Mou, email:mou@phys.nthu.edu.tw
We report a new class of topological superconductivity formed by inter-surface pairing of surface electrons in thin topological insulators. Transport measurements of single crystal Sb2Te3 nanoflakes are performed on samples with thickness of 5-9 quintuple layers (QLs) (Batch A) and 11-27 QLs (Batch B). Steep drops of resistivity below 2.5 K are observed for a number of nanoflakes in both batches, manifesting the superconducting transitions. For Batch A samples, we find that without structural changes, as the thickness of nanoflakes is less than 9 QLs, superconductivity starts to emerge with significant increases of critical currents and critical fields. Theoretical analyses indicate that in contrast to the intra-surface superconductivity of nanoflakes with d ≧ 11 QLs, the strong thickness dependence below 9 QLs is originated from the hybridization of two surface Dirac cones. Our results indicate that the emergent superconductivity below 9 QLs is dominated by p-wave and illuminate a new path to topological superconductivity.

Keywords: topological superconductor, triplet pairing, p-wave