Nonsinusoidal current-phase relations in semiconductor-superconductor-ferromagnetic insulator devices

TL;DR

This paper explores semiconductor-superconductor-ferromagnetic insulator Josephson junctions, demonstrating controllable nonsinusoidal current-phase relations, supercurrent reversal at phase transitions, and a gate-tunable Josephson diode effect with high efficiency.

Contribution

It introduces a novel heterostructure design enabling control over supercurrent harmonics and demonstrates a gate-tunable Josephson diode effect in these devices.

Findings

Control over supercurrent harmonics via gate and magnetization tuning.

Observation of 0–π phase transition leading to supercurrent reversal.

Demonstration of a gate-tunable Josephson diode effect with up to 30% efficiency.

Abstract

Coherent tunneling processes of multiple Cooper pairs across a Josephson junction give rise to higher harmonics in the current phase relation. In this work, we propose and study Josephson junctions based on semiconductor-superconductor-ferromagnetic insulator heterostructures to engineer nonsinusoidal current-phase relations. The gate-tunability of charge carriers density in the semiconductor, together with the adjustable magnetization of the ferromagnetic insulator, provides control over the content of the supercurrent harmonics. At finite exchange field, hybrid junctions can undergo a 0\,--\,$\pi$ phase transition, resulting in the supercurrent reversal. Close to the transition, single-pair tunneling is suppressed and the current-phase relation is dominated by the second-harmonic, indicating transport primarily by pairs of Cooper pairs. Finally, we demonstrate that non-collinear magnetization or spin-orbit coupling in the leads and the junction can lead to a gate-tunable Josephson diode effect with efficiencies of up to $\sim30\%$.