Proximity-induced Superconductivity in Topological Insulator/Superconductor Heterostructures

The exploration of superconductivity in helical Dirac fermions is strongly motivated by scenarios for realizing exotic quantum states in condensed matter. Examples include Majorana modes [1] and supersymmetry [2]. Motivated by such proposals, we are pursuing the development of epitaxially grown heterostructures wherein we attempt to induce superconductivity in the surface states of a three dimensional topological insulator thin film when interfaced with both conventional [3] and unconventional [4] superconductors. This talk will provide an overview of the materials synthesis challenges in this context and discuss the picture of induced superconductivity (or lack thereof) that emerges from angle-resolved photoemission spectroscopy [3,4], point contact Andreev reflection spectroscopy [5] and tunneling spectroscopy.\\ Work done in collaboration with A. Richardella, S.-Y. Xu, M. Z. Hasan, M. Gilbert, F.-C. Chou, G. Gu, W.-Q. Dai and Qi Li.\\ 1. X.-L. Qi and S.-C. Zhang, Rev. Mod. Phys. {\bf 83} 1057 (2011).\\ 2. T. Grover, D. N. Sheng, A. Vishwanath, Science {\bf 344}, 280 (2014).\\ 3. S.-Y. Xu {\it et al.}, Nature Physics {\bf 10}, 943 (2014).\\ 4. S.-Y. Xu {\it et al.}, Phys. Rev. B {\bf 90}, 085128 (2014).\\ 5. W.-Q. Dai {\it et al.}, in preparation.