Luttinger liquid in contact with a Kramers pair of Majorana bound states

TL;DR

This paper investigates how a Kramers pair of Majorana modes influences electron transport in a quantum spin Hall system, revealing interaction-dependent signatures and a critical point in the system's behavior.

Contribution

It introduces a detailed analysis of Majorana modes in quantum spin Hall systems, highlighting the role of interactions and identifying a non-trivial critical point.

Findings

Moderate repulsive interactions stabilize Andreev transmission.

Interactions lead to a non-trivial critical point.

Signatures of Majorana modes depend on interaction strength.

Abstract

We discuss the signatures of a Kramers pair of Majorana modes formed in a Josephson junction on top of a quantum spin Hall system. We show that, while ignoring interactions on the quantum spin Hall edge allows arbitrary Andreev process in the system, moderate repulsive interactions stabilize Andreev transmission - the hole goes into the opposite lead from where the electron has arrived. We analyze the renormalization group equations and deduce the existence of a non-trivial critical point for sufficiently strong interactions.