Super-Hard induced gap in InSb nanowires

In recent years, Majorana bound states were observed experimentally in InSb nanowire-superconductor hybrid devices, which manifested themselves as a zero-bias conductance peak (ZBP). However, there was still significant conductance inside the superconducting gap, which would smear sub-gap features. Moreover, fermionic states inside the gap would also break topological protection. Therefore, a hard gap is required in search of more deterministic signatures of Majorana bound states, and building up Majorana qubits. We report the observation of a hard induced gap in an InSb Josephson junction with an optimized superconducting contact recipe. The gap is resolved in magnetic field up to 2 Tesla, and demonstrates a peculiar kinked field dependence. In addition, we observed rich sub-gap features: Andreev levels appeared close to pinch off regime, while multiple Andreev reflection appeared in open regime.