Andreev-Enhanced Conductance in a Bilayer Graphene Quantum Point Contact
Abstract
Quantum point contacts provide a platform for probing mode-dependent Andreev reflection. Here, we demonstrate Andreev-enhanced conductance in a gate-defined bilayer graphene quantum point contact coupled to a superconducting aluminum electrode. Electrostatic gating enables sequential mode occupation, verified by normal-state conductance quantization. In the superconducting state, the conductance is enhanced within the conductance plateaus, while the enhancement decreases between plateaus, consistent with the nonlinear transmission dependence of Andreev reflection. The enhancement yields effective transmission probabilities up to 0.9, and extends over a bias window of approximately 140 μV, which we associate with a proximity-induced superconducting gap, close to the gap of the aluminum film. For in-plane fields, the enhancement persists up to the critical field, and the bias window follows the spectral gap predicted by Abrikosov-Gor'kov theory. In contrast, perpendicular fields suppress the enhancement approximately linearly from zero field, deviating from homogeneous pair breaking and indicative of flux penetration.
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BibTeX
@misc{horgan2026andreevenhanced,
title = {{Andreev-Enhanced Conductance in a Bilayer Graphene Quantum Point Contact}},
author = {Emma Horgan and Bernd Aichner and Nadine Omar and Kenji Watanabe and Takashi Taniguchi and Luca Banszerus},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41915},
eprint = {2610.41915},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41915},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Andreev-Enhanced Conductance in a Bilayer Graphene Quantum Point Contact
AU - Emma Horgan
AU - Bernd Aichner
AU - Nadine Omar
AU - Kenji Watanabe
AU - Takashi Taniguchi
AU - Luca Banszerus
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41915
UR - https://arxiv.org/abs/2610.41915
AB - Quantum point contacts provide a platform for probing mode-dependent Andreev reflection. Here, we demonstrate Andreev-enhanced conductance in a gate-defined bilayer graphene quantum point contact coupled to a superconducting aluminum electrode. Electrostatic gating enables sequential mode occupation, verified by normal-state conductance quantization. In the superconducting state, the conductance is enhanced within the conductance plateaus, while the enhancement decreases between plateaus, consistent with the nonlinear transmission dependence of Andreev reflection. The enhancement yields effective transmission probabilities up to 0.9, and extends over a bias window of approximately 140 μV, which we associate with a proximity-induced superconducting gap, close to the gap of the aluminum film. For in-plane fields, the enhancement persists up to the critical field, and the bias window follows the spectral gap predicted by Abrikosov-Gor'kov theory. In contrast, perpendicular fields suppress the enhancement approximately linearly from zero field, deviating from homogeneous pair breaking and indicative of flux penetration.
ER -