Spin triplet superconducting proximity effect in a ferromagnetic semiconductor

TL;DR

This paper demonstrates the first evidence of long-range spin-triplet superconductivity induced in a ferromagnetic semiconductor, marking a significant advancement in understanding unconventional pairing in magnetic materials.

Contribution

It provides the first experimental evidence of proximity-induced spin-triplet superconductivity in a ferromagnetic semiconductor, with a supercurrent reaching about 1 micrometer.

Findings

Supercurrent observed over ~1 micrometer distance

Superconductivity responds to magnetic fields indicating triplet pairing

Progress in inducing superconductivity in magnetic semiconductors

Abstract

Conventional spin-singlet superconductivity that deeply penetrates into ferromagnets is typically killed by the exchange interaction, which destroys the spin-singlet pairs. Under certain circumstances, however, superconductivity survives this interaction by adopting the pairing behavior of spin triplets. The necessary conditions for the emergence of triplet pairs are well-understood, owing to significant developments in theoretical frameworks and experiments. The long-term challenges to inducing superconductivity in magnetic semiconductors, however, involve difficulties in observing the finite supercurrent, even though the generation of superconductivity in host materials has been well-established and extensively examined. Here, we show the first evidence of proximity-induced superconductivity in a ferromagnetic semiconductor (In, Fe)As. The supercurrent reached a distance scale of $\sim 1~\mu$m, which is comparable to the proximity range in two-dimensional electrons at surfaces of pure InAs. Given the long range of its proximity effects and its response to magnetic fields, we conclude that spin-triplet pairing is dominant in proximity superconductivity. Therefore, this progress in ferromagnetic semiconductors is a breakthrough in semiconductor physics involving unconventional superconducting pairing.