Evidence of Cooper pair pumping with combined flux and voltage control

TL;DR

This paper demonstrates experimentally that Cooper pairs can be pumped in a mesoscopic superconducting device using synchronized flux and voltage control, showing quantized current steps indicative of Cooper pair transport.

Contribution

It introduces a novel method of controlling Cooper pair transport via combined flux and voltage signals in a single-island structure, with evidence of quantized charge pumping.

Findings

Pumped current increases in 1e steps due to quasiparticle poisoning.

Charge transport is attributed to Cooper pairs despite quasiparticle effects.

Experimental validation of Cooper pair pumping with combined flux and voltage control.

Abstract

We have experimentally demonstrated pumping of Cooper pairs in a single-island mesoscopic structure. The island was connected to leads through SQUID (Superconducting Quantum Interference Device) loops. Synchronized flux and voltage signals were applied whereby the Josephson energies of the SQUIDs and the gate charge were tuned adiabatically. From the current-voltage characteristics one can see that the pumped current increases in 1e steps which is due to quasiparticle poisoning on the measurement time scale, but we argue that the transport of charge is due to Cooper pairs.