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| Format: | Preprint |
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2026
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| Online-Zugang: | https://arxiv.org/abs/2603.25558 |
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| _version_ | 1866917376742653952 |
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| author | Zhang, Zelei Zhai, Jianxiong Zhang, Yi Yan, Jiawei |
| author_facet | Zhang, Zelei Zhai, Jianxiong Zhang, Yi Yan, Jiawei |
| contents | We propose a many-body mechanism for a strong Josephson diode effect (JDE) in an interacting nanoscale SQUID formed by two parallel quantum dots coupled to superconducting leads. Unlike conventional diode behavior, where nonreciprocity originates from a skewed current-phase relation within a single, continuously evolving ground state, the JDE reported here is \emph{branch selected}: the positive and negative critical currents are optimized on different many-body branches across the $0$-$π$ phase boundary, yielding a substantial enhancement of the diode efficiency. We further show that a \emph{nonlocal} Cooper-pair tunneling channel, which binds the two electrons on different arms, is essential: it reshapes the $0$-$π$ boundary and produces a pronounced ``diode band'' in parameter space, in sharp contrast to the fragile hotspot obtained when only local Cooper-pair transfer is available. While the key physics is captured by an effective model in the superconducting atomic limit, our conclusions remain robust for realistic finite-gap devices, as demonstrated within a generalized atomic-limit framework. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_25558 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Many-body Josephson diode effect in superconducting quantum interferometers Zhang, Zelei Zhai, Jianxiong Zhang, Yi Yan, Jiawei Superconductivity Strongly Correlated Electrons We propose a many-body mechanism for a strong Josephson diode effect (JDE) in an interacting nanoscale SQUID formed by two parallel quantum dots coupled to superconducting leads. Unlike conventional diode behavior, where nonreciprocity originates from a skewed current-phase relation within a single, continuously evolving ground state, the JDE reported here is \emph{branch selected}: the positive and negative critical currents are optimized on different many-body branches across the $0$-$π$ phase boundary, yielding a substantial enhancement of the diode efficiency. We further show that a \emph{nonlocal} Cooper-pair tunneling channel, which binds the two electrons on different arms, is essential: it reshapes the $0$-$π$ boundary and produces a pronounced ``diode band'' in parameter space, in sharp contrast to the fragile hotspot obtained when only local Cooper-pair transfer is available. While the key physics is captured by an effective model in the superconducting atomic limit, our conclusions remain robust for realistic finite-gap devices, as demonstrated within a generalized atomic-limit framework. |
| title | Many-body Josephson diode effect in superconducting quantum interferometers |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2603.25558 |