Transport signatures of a quantum spin Hall - chiral topological superconductor junction

E. G. Novik, B. Trauzettel, P. Recher

Published 2019-04-05Version 1

We investigate transport through a normal-superconductor (NS) junction made from a quantum spin Hall (QSH) system and a chiral topological superconductor (TSC) using a two-dimensional extended four-band model for HgTe-based quantum wells in a magnetic (Zeeman) field and subject to s-wave superconductivity. We show using the Bogoliubov-de Gennes scattering formalism that this structure provides a striking transport signal of a chiral Majorana edge mode. The helical edge states of the QSH side act as modes of spatially separated Kramers pairs that are weakly coupled to the chiral Majorana edge mode on the superconducting side. Due to the finite width of the ribbon geometry, a zero-energy Majorana bound state appears at the NS-interface which we identify via a sharp $2e^2/h$ conductance resonance, that turns over into a quantized $4e^2/h$ conductance signal above the resonance. These signatures are a manifestation of the topological nature of the QSH effect and the TSC.