Supercurrent and Multiple Andreev Reflections in InSb Nanosheet SNS Junctions

In this study, the realization of mesoscopic Josephson junctions based on free-standing InSb nanosheet grown by molecular-beam epitaxy is reported. Below the critical temperature of superconducting aluminium electrodes (approximate to 1.1 K), the high transparency of the contacts gives rise to proximity-induced superconductivity. A dissipationless supercurrent which can be modulated by a gate voltage acting on the electron density in the nanosheet flows through the superconducting weak links. At finite bias voltage, subharmonic energy-gap structures (SGS) originating from multiple Andreev reflections (MARs) are observed, indicating a highly transparent InSb nanosheet-superconductor interface. At last, a superconducting hybrid device with niobium electrodes is shown, suitable for further higher temperature and magnetic field transport measurements.