Phase-tunable Majorana bound states in a topological N-SNS junction

TL;DR

This paper investigates how phase bias in a topological nanowire junction influences Majorana modes and conductance, providing theoretical insights into distinguishing topological phases via tunneling spectroscopy.

Contribution

It introduces a theoretical model for phase-tunable Majorana modes in a topological N-SNS junction, highlighting conductance features that differentiate trivial and non-trivial phases.

Findings

Phase-dependent splitting of Majorana modes affects conductance.

Distinct conductance signatures identify topological phases.

Analytical and numerical models agree on key transport features.

Abstract

We theoretically study the differential conductance of a one-dimensional normal-superconductor-normal-superconductor (N-SNS) junction with a phase bias applied between the two superconductors. We consider specifically a junction formed by a spin-orbit coupled semiconducting nanowire with regions of the nanowire having superconducting pairing induced by a bulk $s$-wave superconductor. When the nanowire is tuned into a topologically non-trivial phase by a Zeeman field, it hosts zero-energy Majorana modes at its ends as well as at the interface between the two superconductors. The phase-dependent splitting of the Majorana modes gives rise to features in the differential conductance that offer a clear distinction between the topologically trivial and non-trivial phases. We calculate the transport properties of the junction numerically and also present a simple analytical model that captures the main properties of the predicted tunneling spectroscopy.