Superconducting transport in InAs nanowire double quantum dots

Quantum dot arrays in narrow-gap semiconductors coupled to
superconducting reservoirs can serve as a platform for studying the
interaction between solitary spins and the Cooper pair condensate, which
can give rise to topologically protected Majorana modes.

We define double quantum dots (DQDs) in InAs nanowires with epitaxial
aluminum shell. We demonstrate that we can reach both the strongly and
weakly coupled regimes owing to the five wrap-around electrostatic gates
on the nanowire. We characterize the Josephson coupling via the DQD as a
function of the charge occupation of the islands, and find abrupt
changes which are possible experimental signatures of the change in the
ground state spin configuration of the device. Finite voltage bias
spectroscopy reveals Yu-Shiba-Rusinov states below the superconducting
gap exhibiting the weakly and strongly coupled behavior at different
gate configurations.