Robust one-dimensional proximity superconductivity along graphene domain walls in the quantum Hall regime

Extensive efforts have been undertaken to combine superconductivity and the quantum Hall effect so that Cooper-pair transport between superconducting electrodes in Josephson junctions is mediated by one-dimensional edge states. This interest has been motivated by prospects of finding new physics, including topologically-protected quasiparticles, but also extends into metrology and device applications. So far it has proven challenging to achieve detectable supercurrents through quantum Hall conductors.

I will show that domain walls in minimally twisted bilayer graphene support exceptionally robust proximity superconductivity in the quantum Hall regime, allowing Josephson junctions to operate in fields close to the upper critical field of superconducting electrodes. The critical current is found to be non-oscillatory and practically unchanging over the entire range of quantizing fields, with its value being limited by the quantum conductance of ballistic, strictly one-dimensional electronic channels residing within the domain walls. The system described is unique in its ability to support Andreev bound states at quantizing fields and offers several directions for further exploration.

Reference: J. Barrier et al, Nature 628, 741-745 (2024)

Biography

Dr Julien Barrier’s research activities focus on understanding novel electronic phenomena in moiré superlattices and van der Waals heterostructures, through a combination of quantum transport and photoconductivity experiments. Dr Barrier’s expertise has been internationally recognized through prestigious national and international awards (APS Distinguished Student Award, EPSRC Doctoral Prize Fellowship, Franks Doctoral Prize in Nanoscience and Nanotechnology, IOP’s Thesis prize in superconductivity, etc.). He currently holds a Marie Skłodowska-Curie Actions Postdoctoral Fellowship at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain.