Interplay of superconductivity and ferromagnetism in ferromagnetic semiconductor-based Josephson junctions

TL;DR

This paper demonstrates the integration of superconductivity and ferromagnetism in epitaxial heterostructures, revealing unconventional Josephson effects and nonreciprocal behavior, advancing the development of tunable quantum electronic devices.

Contribution

It introduces epitaxial Al/InAs/(Ga,Fe)Sb heterostructures with atomically abrupt interfaces, enabling exploration of superconducting and ferromagnetic interplay with tunable properties.

Findings

Observation of proximity-induced superconductivity with multiple Andreev reflections

Unconventional Fraunhofer interference patterns with hysteresis and flux jumps

Gate-tunable supercurrents demonstrating semiconducting control

Abstract

The interplay between superconductivity and ferromagnetism has long been pursued as a route to unconventional Josephson effects, yet suitable material platforms remain limited. Here we report Josephson junctions based on epitaxial Al/InAs/(Ga,Fe)Sb heterostructures grown by low-temperature molecular beam epitaxy, achieving atomically abrupt superconductor/semiconductor/ferromagnetic interfaces. The devices exhibit clear proximity-induced superconductivity, including multiple Andreev reflections and gate-tunable supercurrents, confirming transparent coupling across the hybrid structure. Under perpendicular magnetic fields, the junctions reveal highly unconventional Fraunhofer interference patterns with hysteresis, flux jumps, asymmetric lobe evolution, and clear nonreciprocity, providing strong evidence of induced ferromagnetism and broken time-reversal symmetry in the superconducting channel. Gate control further modulates the critical current, highlighting the semiconducting nature of the system. Our results demonstrate that ferromagnetic semiconductor heterostructures can serve as a highly tunable platform for exploring proximity-induced superconductivity and superconducting diode effects, and for advancing device concepts at the intersection of magnetism and quantum electronics.