Realisation of de Gennes’ absolute superconducting switch with a heavy metal interface
- Hisakazu Matsuki
- Alberto Hijano
- Grzegorz P. Mazur
- Stefan Ilić
- Binbin Wang
- Iuliia Alekhina
- Kohei Ohnishi
- Sachio Komori
- Yang Li
- Nadia Stelmashenko
- Niladri Banerjee
- Lesley F. Cohen
- David W. McComb
- F. Sebastián Bergeret
- Guang Yang
- Jason W. A. Robinson
2025-07-01
In 1966, Pierre-Gilles de Gennes proposed a non-volatile mechanism for switching superconductivity on and off in a magnetic device. This involved a superconductor (S) sandwiched between ferromagnetic (F) insulators in which the net magnetic exchange field could be controlled through the magnetisation-orientation of the F layers. Because superconducting switches are attractive for a range of applications, extensive studies have been carried out on F/S/F structures. Although these have demonstrated a sensitivity of the superconducting critical temperature ( T c ) to parallel (P) and antiparallel (AP) magnetisation-orientations of the F layers, corresponding shifts in T c (i.e. Δ T c = T c,AP − T c,P ) are lower than predicted with Δ T c only a small fraction of T c,AP , precluding the development of applications. Here, we report EuS/Au/Nb/EuS structures where EuS is an insulating ferromagnet, Nb is a superconductor and Au is a heavy metal. For P magnetisations, the superconducting state in this structure is quenched down to the lowest measured temperature of 20 mK meaning that Δ T c / T c,AP is practically 1. The key to this so-called 'absolute switching' effect is a sizable spin-mixing conductance at the EuS/Au interface which ensures a robust magnetic proximity effect, unlocking the potential of F/S/F switches for low power electronics.