Evidence for π-Shifted Cooper Quartets and Few-Mode Transport in PbTe Nanowire Three-Terminal Josephson Junctions

Multi-terminal Josephson junctions (MTJJs) have emerged as promising platforms for engineering effective Hamiltonians with non-trivial topologies, such as Weyl crossings and higher-order Chern numbers. The realization of such topological features depends on creating MTJJs with non-classical multi-terminal couplings and where only a few quantum modes are populated. We demonstrate these requirements in a three terminal Josephson junction fabricated on selective-area-grown (SAG) PbTe nanowires. Our measurements reveal signatures of a π-shifted Josephson effect, which is attributed to coherent inter-terminal couplings mediated by correlated four-particle quantum states, known as Cooper quartets. Additionally, we observe supercurrent coexisting with a non-monotonic evolution of conductance as a function of gate voltage, indicating few-mode transport in two- and three-terminal devices.