Magnetotransport Phenomena in Topological Insulator / Superconductor Bi2 Te3/Nb Bilayer and Trilayer Thin Films

Abstract

Bi2Te3 is a three-dimensional topological insulator, whose surface exhibits metallic electronic states, while its bulk is effectively free of mobile charge carriers. These states are formed by topological effects that also render the electrons travelling on such surfaces insensitive to scattering by impurities. Such topological insulators combined with a superconductor may provide new routes to the study of transport through their unconventional surface states. Here, we show transport experiments on Bi2Te3/Nb bilayer and Nb/Bi2Te3/Nb trilayer, a system which is important to investigate the appearance of the predicted Majorana states at the interface between a topological insulator and a superconductor. Interestingly, with the measurements at 3 K we observe that the onset of superconductivity of Nb layer, that is adjacent to the topological insulator, creates novel phenomena that arise from the interplay between a superconductor and a topological insulator with a superconducting state at the surfaces of Bi2Te3. Our results show that Bi2Te3 is a promising material system to get a better understanding of the superconducting proximity effect in topological surface states, and to examine the appearance of zero-energy Majorana states in transport experiments.