Multiply connected electronic networks threaded by flux tubes have been proposed as a platform for adiabatic quantum transport and topological states. Multi-terminal Josephson junction (MTJJ) has been suggested as a pathway to realize this concept. Yet, the manifestations of topology in MTJJ remain open for experimental study. Here, we investigated the artificial topological band structure of three-terminal graphene Josephson junctions. Employing tunnelling spectroscopy and magnetic flux gates, we captured the tomography of the Andreev bound state (ABS) energy spectrum as a function of two independent phase differences. This ABS spectrum exhibits the topological transition from gapped to gapless states, akin to the band structure of nodal-line semimetals. Our results show the potential of graphene-based MTJJs for engineering band topologies in higher dimensions.
@article{arxiv.2411.01170,
title = {Full tomography of topological Andreev bands in graphene Josephson junctions},
author = {Woochan Jung and Seyoung Jin and Sein Park and Seung-Hyun Shin and Kenji Watanabe and Takashi Taniguchi and Gil Young Cho and Gil-Ho Lee},
journal= {arXiv preprint arXiv:2411.01170},
year = {2026}
}