We construct high-quality graphene-based van der Waals devices with narrow superconducting niobium nitride (NbN) electrodes, in which superconductivity and robust fqH coexist. We find crossed Andreev reflection (CAR) across the superconductor separating two fqH edges. Our observed CAR probabilities in the particle-like 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.
@article{arxiv.2009.07836,
title = {Andreev reflection in the fractional quantum Hall state},
author = {Önder Gül and Yuval Ronen and Si Young Lee and Hassan Shapourian and Jonathan Zauberman and Young Hee Lee and Kenji Watanabe and Takashi Taniguchi and Ashvin Vishwanath and Amir Yacoby and Philip Kim},
journal= {arXiv preprint arXiv:2009.07836},
year = {2022}
}
Comments
Revised text, additional main and appendix figures