Public Talk: Superconductivity at the Flick of a Magnetic Switch

ABSTRACT

Spin-orbit interaction and magnetism can control electronic and superconducting behaviour at interfaces between magnetic materials, metals and superconductors [1], opening possibilities for energy-efficient electronic devices. In this lecture I will discuss magnetic and spin-orbit interaction effects at interfaces between the ferromagnetic insulator EuS and adjacent metals of Nb and Au, demonstrating mechanisms for tunable quantum and superconducting transport. In EuS/Au/EuS spin-switches, we observe a crossover from weak localization in ultrathin Au to interfacial giant magnetoresistance as the Au thickness increases. This transition is driven by a proximity-induced magnetic exchange field that suppresses quantum interference and enables spin Hall magnetoresistance—remarkably, without a metallic ferromagnet. In EuS/Au/Nb/EuS superconducting devices, the same interfacial exchange field has enabled the first demonstration of absolute switching of superconductivity [1]: the superconducting state is quenched in the parallel magnetization configuration and restored in the antiparallel state, achieving full on/off control. This effect stems from strong spin-mixing conductance at the EuS/Au interface. Together, these findings show that interfacial spin control in magnetic insulator/metal systems can drive robust switching behaviour, advancing prospects for low-power, non-volatile spintronic technologies.

[1] M Amundsen*, J Linder*, JWA Robinson*, I Žutić, N Banerjee*, Reviews of Modern Physics 96, 021003 (2024).
[2] H Matsuki et al., to appear in Nature Communications (2025).

BIOGRAPHY

Professor Jason Robinson holds a Chair in Materials Physics at the University of Cambridge, where he heads the Department of Materials Science & Metallurgy and directs the Quantum Materials & Devices Group. His transformative research on hybrid superconducting systems includes discovering s-wave spin-triplet Cooper pairs and pioneering the field of superconducting quantum spintronics, merging superconductors with magnets for applications in low power electronic devices. This work extends to quantum matter and spintronic systems. As Co-Director of Cambridge's Centre for Materials Physics, he bridges academia and industry to develop quantum technologies. An elected Fellow of various societies, Robinson combines scientific innovation with mentorship, shaping future leaders in materials science.

Note: A mingling session with faculty members and students will follow the talk at 4 pm in the HKIAS Meeting Room (Academic Exchange Building 024).