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arXiv · 2508.11768

Directional conductance of Andreev crystals in hybrid Josephson junction arrays

Anders Enevold Dahl·Andrea Maiani·Max Geier·Javad Shabani·Karsten Flensberg
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Abstract

Andreev bound states are coherent electron-hole superpositions that form in a normal metal through repeated Andreev reflection at a superconducting interface. When the length of a superconducting segment is comparable to the coherence length, the bound states on opposite sides of the segment hybridize through quasiparticle tunneling. In a periodic array, these hybridized Andreev bound states form energy bands below the superconducting gap. We develop a theoretical framework for transport in such Andreev crystals. We demonstrate that, at high interface transparency, a constant phase bias between neighboring superconductors renders the bands directional: one band contains only right-moving and the other only left-moving electronic states. This property leads to a directional conductance that enables the device to operate as a flux- and bias-voltage-tunable filter that allows signal transmission in only one direction.

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Anders Enevold Dahl, Andrea Maiani, Max Geier, Javad Shabani, Karsten Flensberg. 2025-08-15. Directional conductance of Andreev crystals in hybrid Josephson junction arrays. https://doi.org/10.1103/zrt6-971d

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