Enhancing the Josephson diode effect with Majorana bound states

TL;DR

This paper demonstrates that Majorana bound states in topological superconductors can enhance the Josephson diode effect by creating asymmetric current-phase relations, with potential applications in superconducting electronics.

Contribution

It reveals how Majorana bound states in topological phases amplify the Josephson diode effect through asymmetric Andreev spectra in phase-biased junctions.

Findings

Josephson diode effect is enhanced in topological phases with Majorana states.

Asymmetry in current-phase relations is linked to Majorana-induced nonlocality.

The effect persists even in trivial phases, but is significantly stronger in topological regimes.

Abstract

We consider phase-biased Josephson junctions with spin-orbit coupling under external magnetic fields and study the emergence of the Josephson diode effect in the presence of Majorana bound states. We show that junctions having middle regions with Zeeman fields along the spin-orbit axis develop a low-energy Andreev spectrum that is asymmetric with respect to the superconducting phase difference $\phi=\pi$, which is strongly influenced by Majorana bound states in the topological phase. This asymmetric Andreev spectrum gives rise to anomalous current-phase curves and critical currents that are different for positive and negative supercurrents, thus signaling the emergence of the Josephson diode effect. While this effect exists even in the trivial phase, it gets enhanced in the topological phase due to the spatial nonlocality of Majorana bound states. Our work thus establishes the utilization of topological superconductivity for enhancing the functionalities of Josephson diodes.