Majorana splitting from critical currents in Josephson junctions

TL;DR

This paper explores how critical currents in Josephson junctions with proximitized nanowires reveal signatures of Majorana zero modes and topological phase transitions, providing a new method to detect and study Majoranas.

Contribution

It demonstrates that critical current measurements in short Josephson junctions can indicate topological transitions and Majorana interference, offering a tunable alternative to traditional detection methods.

Findings

Critical currents show signatures of topological phase transition.

Oscillatory patterns in critical currents indicate Majorana interference.

Tuning junction transmission modifies Majorana signatures.

Abstract

A semiconducting nanowire with strong Rashba spin-orbit coupling and coupled to a superconductor can be tuned by an external Zeeman field into a topological phase with Majorana zero modes. Here we theoretically investigate how this exotic topological superconductor phase manifests in Josephson junctions based on such proximitized nanowires. In particular, we focus on critical currents in the short junction limit ($L_{\rm N}\ll \xi$, where $L_{\rm N}$ is the junction length and $\xi$ is the superconducting coherence length) and show that they contain important information about nontrivial topology and Majoranas. This includes signatures of the gap inversion at the topological transition and a unique oscillatory pattern that originates from Majorana interference. Interestingly, this pattern can be modified by tuning the transmission across the junction, thus providing complementary evidence of Majoranas and their energy splittings beyond standard tunnel spectroscopy experiments, while offering further tunability by virtue of the Josephson effect.