Colossal superconducting spin-valve effect in superconductor-non-magnetic metal heterostructure mediated by spin–orbit coupling

Abstract

Nb/Pt and Nb/Cu nanohybrids were sputtered on Si(100) substrate and systematically studied by transmission electron microscopy and magneto-transport measurements. Our experimental findings show that the colossal spin-valve effect measured in a hybrid formed by thick Pt layers deposited on Nb films is absent in equivalent Nb/Cu nanohybrids. In the latter, an ordinary spin-valve effect was experimentally measured and numerically quantified using the superconducting anisotropic phenomenon based on the Ginzburg–Landau model. The unusual enhancement of the spin-valve effect is explained considering the formation of odd-frequency triplet states of Cooper pairs at the Nb/Pt interface induced by the spin–orbit coupling of the Pt component. In a broad perspective, this study strongly evidences the role that the spin–orbit interaction can play for controlling the spin state of Cooper pairs at interfaces of superconductor-based hybrids in the absence of ferromagnetic materials.