Magnetic field enhanced critical current in Ge–Si nanowire Josephson junctions

Abstract

Anomalous critical current enhancement was observed with increasing magnetic field in Josephson junctions based on Ge–Si core-shell nanowires. Despite the predicted topological properties of these nanowires, which could potentially lead to non-trivial superconducting order parameter symmetries, our investigation unveils a more generalized, non-topological explanation for the observed critical current enhancement in these devices. Our findings suggest that the enhancement arises from a thermalization process induced by the magnetic field, wherein in-gap quasiparticles are generated. These quasiparticles play a crucial role in enhancing the cooling of the device, thereby lowering the effective temperature and resulting in an increased critical current. Furthermore, we elucidate how this thermalization effect varies with device geometry and measurement configuration.