Majorana Kramers pairs in Rashba double nanowires with interactions and disorder

TL;DR

This paper investigates how electron-electron interactions and disorder influence the stability of Majorana Kramers pairs in Rashba double nanowires coupled to an s-wave superconductor, identifying conditions for their robustness.

Contribution

It provides a detailed phase diagram showing the stability regimes of Majorana Kramers pairs considering interactions and disorder, using both bosonization and microscopic approaches.

Findings

Interactions can stabilize Majorana Kramers pairs.

Strong electron-electron interactions are needed to reach the topological phase.

Disorder effects are analyzed and incorporated into the phase diagram.

Abstract

We analyze the effects of electron-electron interactions and disorder on a Rashba double-nanowire setup coupled to an s-wave superconductor, which has been recently proposed as a versatile platform to generate Kramers pairs of Majorana bound states in the absence of magnetic fields. We identify the regime of parameters for which these Kramers pairs are stable against interaction and disorder effects. We use bosonization, perturbative renormalization group, and replica techniques to derive the flow equations for various parameters of the model and evaluate the corresponding phase diagram with topological and disorder-dominated phases. We confirm aforementioned results by considering a more microscopic approach which starts from the tunneling Hamiltonian between the three-dimensional s-wave superconductor and the nanowires. We find again that the interaction drives the system into the topological phase and, as the strength of the source term coming from the tunneling Hamiltonian increases, strong electron-electron interactions are required to reach the topological phase.