Searching for signatures of non-trivial topology in diffusive multiterminal Josephson junctions

Multi-terminal Josephson junctions (MTJJs), or devices with a ballistic normal metal with n superconducting contacts, have been proposed as artificial analogs of topological n − 1 dimensional crystals, with the phase difference φ between two superconductors playing the role of the wave vector k in a crystal.  Topological behavior has also been predicted for diffusive MTJJs, where a diffusive normal metal is placed in contact with multiple superconducting contacts.2 Here we report measurements of the resistance of diffusive 3-terminal MTJJs as a function of the phase differences between the superconductors.  The resistance shows a rich periodic structure that reflects the opening and closing of gaps in the excitation spectrum of quasiparticles resulting from the modulation of the phase differences between the superconductors.

*M. Wisne, Y. Deng, M. Lilja, P. Hakonen and V. Chandrasekhar. Mapping the topological proximity-induced gap of multiterminal Josephson junctions, arXiv:2408.09023.