Realisation of de Gennes' absolute superconducting switch with a heavy metal interface.
basic_science · Level V
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- Record sourced from PubMed, PMID 40595601.
- Also identified by DOI 10.1038/s41467-025-61267-2 and PMC identifier 12218286.
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Abstract
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<sub>c</sub>) to parallel (P) and antiparallel (AP) magnetisation-orientations of the F layers, corresponding shifts in T<sub>c</sub> (i.e. ΔT<sub>c</sub> = T<sub>c,AP</sub> - T<sub>c,P</sub>) are lower than predicted with ΔT<sub>c</sub> only a small fraction of T<sub>c,AP</sub>, 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 ΔT<sub>c</sub>/T<sub>c,AP</sub> 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.