3e tunneling processes in a superconducting single-electron tunneling transistor

TL;DR

This paper reports the observation of a novel three-electron charge tunneling process in a superconducting single-electron transistor, involving simultaneous tunneling of a Cooper pair and a quasiparticle across separate barriers.

Contribution

It demonstrates the existence of a three-electron tunneling process involving Cooper pairs and quasiparticles in a superconducting SET, expanding understanding of tunneling mechanisms.

Findings

Observation of three-electron tunneling current.

Tunneling involves Cooper pairs and quasiparticles across separated barriers.

Process occurs in Coulomb blockade regime.

Abstract

A current due to a tunneling event that involves three times the charge of an electron was observed in the current - voltage characteristics of a superconducting single-electron tunneling transistor. In this tunnel event, a Cooper pair tunnels through one tunnel barrier simultaneously with a quasiparticle that tunnels through a second tunnel barrier which is about 0.5 microns distant from the first tunnel barrier. This current was observed in a bias regime where current flow due to sequential quasiparticle tunneling is forbidden due to the Coulomb blockade.