Tuning Yu-Shiba-Rusinov states in a quantum dot

Nanowire/superconductor hybrid devices are important systems that are currently used in many experimental programs. In these systems, deliberate or accidental quantum dots in the nanowire create Yu-Shiba-Rusinov subgap states when they couple to the superconductor. In this work, an array of bottom gates under an InAs nanowire is used to tune the coupling (ΓS) of individual quantum states to a superconductor as the system is probed with a weakly coupled normal lead. The paper includes measurements of a coupling-induced quantum phase transition as well as the Zeeman splitting of a subgap state for different values of ΓS. The authors analyze their data using an extension of the Anderson model and the numerical renormalization group procedure and give quantitative values for key parameters of the system.