Tunneling spectroscopy of Andreev bands in multiterminal graphene-based Josephson junctions.

Jung, Woochan; Jin, Seyoung; Park, Sein; Shin, Seung-Hyun; Watanabe, Kenji; Taniguchi, Takashi; Cho, Gil Young; Lee, Gil-Ho · Sci Adv · 2025

basic_science · Level V

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Abstract

Multiply connected electronic networks threaded by flux tubes have been proposed as a platform for adiabatic quantum transport and topological states. Multiterminal 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. Using tunneling spectroscopy and magnetic flux gates, we performed a direct mapping of the Andreev bound state (ABS) energy spectrum as a function of two independent phase differences. This ABS spectrum exhibits the transition between gapped states associated with different topological invariants. Our results show the potential of graphene-based MTJJs for engineering band topologies in higher dimensions.