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

## TL;DR

This paper explores how transport measurements in a quantum spin Hall system coupled with a chiral topological superconductor reveal signatures of topological phases, including conductance plateaux indicative of non-trivial and trivial topological states.

## Contribution

It demonstrates the transport signatures of a 2D chiral topological superconductor in a QSH system using a detailed four-band model and scattering formalism, highlighting topological phase transitions.

## Key findings

- Conductance resonances alternate between 2e^2/h and 4e^2/h plateaux.
- Signatures correlate with the non-zero Chern number in the 2D limit.
- Transport signals reflect the topological nature of the QSH and TSC.

## Abstract

We investigate transport through a normal-superconductor (NS) junction made from a quantum spin Hall (QSH) system with helical edge states and a two-dimensional (2D) chiral topological superconductor (TSC) having a chiral Majorana edge mode. We employ 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 2D TSC. As a function of the sample width (or Fermi energy) the conductance resonances go through a sequence of $2e^2/h$ (non-trivial phase) and $4e^2/h$ plateaux (trivial phase) which fall within the region of a non-zero Chern number (2D limit) as the sample width becomes large. These signatures are a manifestation of the topological nature of the QSH effect and the TSC.