Signatures of topological superconductivity in quantum spin Hall/superconductor  junctions

Shu-Ping Lee
Dept Physics, CalTech.

Quantum spin Hall-superconductor hybrids are promising sources of topological superconductivity and Majorana modes, particularly given recent progress on HgTe and InAs/GaSb.  I propose a new method of    revealing topological  superconductivity in extended quantum spin Hall Josephson junctions supporting `fractional  Josephson currents'.   Specifically, I show that as one threads magnetic flux between the superconductors, the critical current traces an interference pattern featuring sharp fingerprints of topological superconductivity---even  when noise spoils parity  conservation. This system becomes more interesting as interactions between electrons are    involved. I use   renormalization group methods to extract universal transport characteristics of     superconductor/quantum spin Hall   heterostructures where the native edge states serve as a lead. Interestingly, arbitrarily weak interactions induce     qualitative changes in the behavior relative to the free-fermion limit, leading to a sharp   dichotomy in conductance   for the trivial (narrow superconductor) and topological (wide superconductor) cases.