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arXiv · 2601.08637

Coupling of Klein-Andreev Resonant States in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$-graphene-Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ Devices

Sharadh Jois·Jose L. Lado·Genda Gu·Qiang Li·Ji Ung Lee
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Abstract

Quantum devices require coherent coupling over macroscopic distances. Recently, resonances due to Klein tunneling and Andreev reflection states (KARS) have been observed in a naturally occurring p-n junction at the interface between Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO), a high-Tc superconductor (HTS), and graphene. The resonances appear as conductance oscillations with gating. Here, we show coupling between the KARS in BSCCO-graphene-BSCCO devices of varying separation (L). The coupling is evidenced by a power-law decay of resonance period as L increases from tens of nanometers to single microns. These results demonstrate the long-distance coupling of KARS cavities in graphene-HTS junctions. The length dependence seen in experiments is supported by single-particle spectral functions which show KARS are coupled by transport modes in graphene. The strong coupling between KARS in BSCCO-graphene-BSCCO junctions showcases the novelty of HTS-graphene junctions for quantum circuits and unconventional Josephson junctions.

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Sharadh Jois, Jose L. Lado, Genda Gu, Qiang Li, Ji Ung Lee. 2026-01-13. Coupling of Klein-Andreev Resonant States in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$-graphene-Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ Devices. https://doi.org/10.1103/m56s-hcdq

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