Physics Colloquium: Topologically non-trivial superconducting systems

There has been great interest in novel materials demonstrating exotic quantum phases of matter, such as three-dimensional topological insulators. These materials are characterized by an insulating bulk surrounded by two-dimensional conducting surface states that are protected by time-reversal symmetry. Topological insulators can be transformed into exotic superconductors with unconventional pairing by either coupling them with s-wave superconductors or chemically doping them. The resulting systems host zero-energy quasiparticle excitations called Majorana bound states, which can robustly store quantum information and potentially revolutionize quantum computation. In the first part of my talk, I will discuss measurements of Josephson junctions with topological insulator weak links such as Bi2Se3. Investigations of such topological junctions in superconducting quantum interference devices (SQUIDs) reveal an anomalous supercurrent that is carried by low-energy surface bound states. In the second part, I will discuss our preliminary results on Andreev reflection spectroscopy of Nb doped Bi2Se3 in the context of p-wave pairing gap in superconducting doped topological insulators. The measurements point toward the realization of topological superconductivity and topological quantum computation.