Coupling of Klein-Andreev resonant states in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">B</mi><msub><mi mathvariant="normal">i</mi><mn>2</mn></msub><mi mathvariant="normal">S</mi><msub><mi mathvariant="normal">r</mi><mn>2</mn></msub><mi>CaC</mi><msub><mi mathvariant="normal">u</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mrow><mn>8</mn><mo>+</mo><mi>x</mi></mrow></msub></mrow></math>-graphene-<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">B</mi><msub><mi mathvariant="normal">i</mi><mn>2</mn></msub><mi mathvariant="normal">S</mi><msub><mi mathvariant="normal">r</mi><mn>2</mn></msub><mi>CaC</mi><msub><mi mathvariant="normal">u</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mrow><mn>8</mn><mo>+</mo><mi>x</mi></mrow></msub></mrow></math> devices

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

doi:10.1103/m56s-hcdq

Coupling of Klein-Andreev resonant states in $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ -graphene- $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ devices

Sharadh Jois ^1,*,†, Jose L. Lado ³, Genda Gu⁴, Qiang Li ^4,5, and Ji Ung Lee^1,2,‡

¹College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203, USA
²College of Nanotechnology, Science, and Engineering, University at Albany, SUNY, New York 12203, USA
³Department of Applied Physics, Aalto University, 00076 Aalto, Espoo, Finland
⁴Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973, USA
⁵Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA

^*Present Address: Laboratory for Physical Sciences, 8050 Greenmead Dr, College Park, Maryland 20740.
^†Contact author: sjois@lps.umd.edu
^‡Contact author: jlee1@albany.edu

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Phys. Rev. B 113, 035410 – Published 6 January, 2026

DOI: https://doi.org/10.1103/m56s-hcdq

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 $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ (BSCCO), a $high − T_{c}$ 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 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 devices showcases the possibility of HTS-graphene junctions for quantum circuits and unconventional Josephson junctions.

Physical Review B

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Coupling of Klein-Andreev resonant states in $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ -graphene- $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ devices

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Coupling of Klein-Andreev resonant states in Bi2Sr2CaCu2O8+x-graphene-Bi2Sr2CaCu2O8+x devices

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Coupling of Klein-Andreev resonant states in $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ -graphene- $B i_{2} S r_{2} CaC u_{2} O_{8 + x}$ devices