High-field Josephson effect enabled by a moir\'e Hofstadter spectrum

A. Díez-Carlón; M. Cárdenes Wuttig; N. Wei; D. Ivanov; P. Altpeter; P. Hakonen; K. Watanabe; T. Taniguchi; L. I. Glazman; D. K. Efetov

arXiv · 2607.11721

High-field Josephson effect enabled by a moir\'e Hofstadter spectrum

A. Díez-Carlón·M. Cárdenes Wuttig·N. Wei·D. Ivanov·P. Altpeter·P. Hakonen·K. Watanabe·T. Taniguchi·L. I. Glazman·D. K. Efetov

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Abstract

Magnetic fields generally suppress phase-coherent Josephson transport, limiting superconducting interferometry to relatively low fields. Here we show that moir\'e-engineered graphene Josephson junctions can overcome this constraint. Using ballistic graphene/hBN junctions, we establish phase-coherent Andreev transport through Fabry-P\'erot oscillations and Fraunhofer interference that persist across both the primary Dirac cone and reconstructed moir\'e minibands. We then demonstrate phase-coherent Josephson interference up to 6 T in the fractal Hofstadter-butterfly regime, well beyond the range expected for conventional ballistic graphene junctions. Comparison with Hofstadter-spectrum calculations reveals that superconductivity survives where the moir\'e potential transforms Landau levels with quenched group velocity into dispersive magnetic Bloch bands with finite quasiparticle group velocity, enabling extended electron-hole Andreev trajectories across the junction. Our results show that Hofstadter minibands can stabilize phase-coherent superconductivity deep into the parameter domain conventionally associated with the quantum Hall regime, establishing a new platform for high-field superconducting interferometry.

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A. Díez-Carlón, M. Cárdenes Wuttig, N. Wei, D. Ivanov, P. Altpeter, P. Hakonen, K. Watanabe, T. Taniguchi, L. I. Glazman, D. K. Efetov. 2026-07-13. High-field Josephson effect enabled by a moir\'e Hofstadter spectrum. https://arxiv.org/abs/2607.11721

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