Coherent Subgap Transport in Spin-Split Josephson Junctions
David Caldevilla-Asenjo, Gorm Ole Steffensen, Sara Catalano, Alberto Hijano, Maxim Ilyn, Celia Rogero, Ramon Aguado, F. Sebastian Bergeret, Alfredo Levy Yeyati
DOI 10.1103/lt7q-6ff3 · Physical Review Letters
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Abstract
We report the first experimental observation of subgap transport in ferromagnetic insulator–superconductor–insulator–superconductor junctions realized in EuS/Al/AlOx/Al vertical stacks. Differential conductance measurements reveal multiple Andreev reflection peaks, with odd-order peaks split by the spin-splitting induced in the superconductor adjacent to EuS, while even-order peaks remain unaffected. Combining experiments with quasiclassical transport modeling, we extract the spin-splitting and an approximate distribution of transmission channels, finding that roughly a hundred highly transmitting (τ>0.3) channels will dominate transport. The observation of a Josephson current further confirms strong superconducting coupling through these channels. Our results demonstrate that a single spin-split superconductor is sufficient to observe the even-odd multiple Andreev reflection effect. Our work establishes EuS/Al junctions as a versatile platform to study subgap transport, Josephson coupling, and spin-polarized superconducting phenomena.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.45 | Pressure not reported | onset |
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