Coherent subgap transport in spin-split Josephson junctions
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866914173994139648 |
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| author | Caldevilla-Asenjo, David Steffensen, Gorm Ole Catalano, Sara Hijano, Alberto Ilyn, Maxim Rogero, Celia Aguado, Ramon Bergeret, F. Sebastian Yeyati, Alfredo Levy |
| author_facet | Caldevilla-Asenjo, David Steffensen, Gorm Ole Catalano, Sara Hijano, Alberto Ilyn, Maxim Rogero, Celia Aguado, Ramon Bergeret, F. Sebastian Yeyati, Alfredo Levy |
| contents | 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 the distribution of transmission channels, finding that a significant fraction ($\sim 23\%$) of highly transparent channels ($τ\approx 0.9$) dominates 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 MAR effect. Our work establishes EuS/Al junctions as a versatile platform to study subgap transport, Josephson coupling, and spin-polarized superconducting phenomena. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_23359 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Coherent subgap transport in spin-split Josephson junctions Caldevilla-Asenjo, David Steffensen, Gorm Ole Catalano, Sara Hijano, Alberto Ilyn, Maxim Rogero, Celia Aguado, Ramon Bergeret, F. Sebastian Yeyati, Alfredo Levy Superconductivity 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 the distribution of transmission channels, finding that a significant fraction ($\sim 23\%$) of highly transparent channels ($τ\approx 0.9$) dominates 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 MAR effect. Our work establishes EuS/Al junctions as a versatile platform to study subgap transport, Josephson coupling, and spin-polarized superconducting phenomena. |
| title | Coherent subgap transport in spin-split Josephson junctions |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2511.23359 |