Interplay of charge and vorticity quantization in superconducting Coulomb blockaded island

TL;DR

This paper explores how vorticity in a small superconducting island influences charge transfer, revealing a strong interplay between rotational states and charge dynamics, with potential for experimental charge pumping measurements.

Contribution

It demonstrates the impact of vortex vorticity on the charge transfer spectrum in superconducting islands and proposes a method to measure this interaction via charge pumping.

Findings

Vorticity affects the quantum spectrum of electron-hole excitations.

Vortices can host an additional electron, altering the parity effect.

Charge pumping can be used to detect vorticity-charge interaction.

Abstract

The angular momentum or vorticity of Cooper pairs is shown to affect strongly the charge transfer through a small superconducting (S) island of a single electron transistor. This interplay of charge and rotational degrees of freedom in a mesoscopic superconductor occurs through the effect of vorticity on the quantum mechanical spectrum of electron-hole excitations. The subgap quasiparticle levels in vortices can host an additional electron, thus, suppressing the so-called parity effect in the S island. We propose to measure this interaction between the quantized vorticity and electric charge via the charge pumping effect caused by alternating vortex entry and exit controlled by a periodic magnetic field.