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Résumé |
The superconducting proximity effect is the underlying mechanism of topologically non-trivial boundary
states, like Majorana bound states, in semiconducting nanowires with a large spin orbit interaction. These
protected states are potentially useful for quantum information technologies. However, spectroscopy of these
states is challenging because of the poor energetic and spatial control of conventional tunnel barriers,
defined by electrostatic gates. Here, we report electronic spectroscopy measurements of the proximity gap in
a semiconducting indium arsenide nanowire segment coupled to a superconductor using a spatially separated
quantum dot formed deterministically by crystal phase engineering. We extract the characteristic parameters
of the proximity induced gap, which is suppressed for lower electron densities and fully evolved for larger
ones. We understand this gate-tunable transition of the proximity effect as a transition from the long to the
short junction regime of subgap bound states in the NW segment. Our device architecture opens up a way to
systematic, unambiguous spectroscopy studies of subgap bound states, such as Majorana bound states. |
