Gil-Ho Lee

Andreev bands in three-terminal graphene Josephson junctions

Multiply connected electronic networks were proposed as a potential platform for studying adiabatic quantum transport properties, which are closely linked to topological invariants [1]. This concept could be realized in multi-terminal Josephson junctions (MTJJs). In this work, we investigate the artificial topological band structure of three-terminal graphene Josephson junctions by using superconducting tunneling spectroscopy. Differential tunnelling conductance shows the characteristic features of Andreev bound states (ABS) formed in the graphene. We controlled the superconducting phase configurations by applying the flux gates and obtained the ABS energy spectrum as a function of two independent phase differences and energy. Such quasi-momentum v.s. energy map of ABS unveils the transition between gapped and gapless states, which corresponds to the topological band structure of 2D-Dirac semimetals. Our results show the potential of graphene based MTJJ for engineering the band topology.

[1] J.E Avron Rev. Mod. Phys., 60, 873 (1988).

[2] Roman-Pascal Riwar, Manuel Houzet, Julia S.Meyer & Yuli V. Nazarov. Nature Comm. 7, 11167 (2016)

Three-terminal Graphene Josephson junction with flux control lines