Electrostatic control of quasiparticle poisoning in a hybrid semiconductor-superconductor island

TL;DR

This paper demonstrates how electrostatic gates can precisely control quasiparticle poisoning in a hybrid nanowire device, significantly affecting charge tunneling rates and providing insights into superconducting gap properties.

Contribution

It introduces a method for electrostatic control of quasiparticle poisoning in hybrid nanowire devices, revealing gate-dependent tunneling behavior and superconducting gap characteristics.

Findings

Electrostatic gates can change tunneling rates by two orders of magnitude.

Gate dependence affects the size and softness of the induced superconducting gap.

Temperature and magnetic field influence tunneling rates.

Abstract

The performance of superconducting devices is often degraded by the uncontrolled appearance and disappearance of quasiparticles, a process known as poisoning. We demonstrate electrostatic control of quasiparticle poisoning in the form of single-charge tunneling across a fixed barrier onto a Coulomb island in an InAs/Al hybrid nanowire. High-bandwidth charge sensing was used to monitor charge occupancy of the island across Coulomb blockade peaks, where tunneling rates were maximal, and Coulomb valleys, where tunneling was absent. Electrostatic gates changed on-peak tunneling rates by two orders of magnitude for a barrier with fixed normal-state resistance, which we attribute to gate dependence of the size and softness of the induced superconducting gap on the island, corroborated by separate density-of-states measurements. Temperature and magnetic field dependence of tunneling rates are also investigated.