Periodicity transition of Coulomb oscillation in hybrid superconductor-semiconductor (Pb-InSb) system

Because of the Cooper pair transport, the oscillation of charge electron of superconducting ground state is always 2e^- periodic in an island with quantized electrons. The transition from 2e^- to 1e^- periodicity has been explored in different superconductor-semiconductor system when an external magnetic field or bias voltage is applied. But it hasn't been reported in the hybrid Pb-InSb structure yet. Comparing with other superconductor like Aluminum, Lead has a larger energy gap which is up to ~2.7meV and potentially leads to a larger topological gap. We observed an even-odd split at finite bias voltage, indicating the hard superconducting gap. Pb-InSb-Pb Josephson junction also shows the hard superconducting gap in the tunneling limit.