Andreev Reflection in the Fractional Quantum Hall State

Önder Gül; Yuval Ronen; Si Young Lee; Hassan Shapourian; Jonathan Zauberman; Young Hee Lee; Kenji Watanabe; Takashi Taniguchi; Ashvin Vishwanath; Amir Yacoby; Philip Kim

doi:10.1103/physrevx.12.021057

ジャーナル論文 Andreev Reflection in the Fractional Quantum Hall State

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Önder Gül, Yuval Ronen, Si Young Lee, Hassan Shapourian, Jonathan Zauberman, Young Hee Lee, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Amir Yacoby, Philip Kim. Andreev Reflection in the Fractional Quantum Hall State. Physical Review X. 2022, 12 (2), 021057. https://doi.org/10.1103/physrevx.12.021057

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(abstract)

We construct high-quality graphene-based van der Waals devices with narrow superconducting niobium nitride (NbN) electrodes, in which superconductivity and a robust fractional quantum Hall (FQH) state coexist. We find a possible signature for crossed Andreev reflection (CAR) across the superconductor separating two FQH edges. Our observed CAR probabilities in the particlelike fractional fillings are markedly higher than those in the integer and hole-conjugate fractional fillings and depend strongly on temperature and magnetic field unlike the other fillings. Further, we find a filling-independent CAR probability in integer fillings, which we attribute to spin-orbit coupling in NbN allowing for Andreev reflection between spin-polarized edges. These results provide a route to realize novel topological superconducting phases in FQH-superconductor hybrid devices based on graphene and NbN.

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