Cooling of a suspended nanowire by an AC Josephson current flow

TL;DR

This paper demonstrates that a suspended nanowire in a Josephson junction can be cooled via an applied DC bias, transferring vibrational energy to electronic states, achieving near ground-state vibration suppression.

Contribution

It introduces a novel self-cooling mechanism for nanowire vibrations using AC Josephson current flow in a nanoelectromechanical system.

Findings

Cooling reduces vibrational occupation number to ~0.1

Effective energy transfer from vibronic to electronic states

Feasible with metallic carbon nanotube nanowires

Abstract

We consider a nanoelectromechanical Josephson junction, where a suspended nanowire serves as a superconducting weak link, and show that an applied DC bias voltage an result in suppression of the flexural vibrations of the wire. This cooling effect is achieved through the transfer of vibronic energy quanta first to voltage driven Andreev states and then to extended quasiparticle electronic states. Our analysis, which is performed for a nanowire in the form of a metallic carbon nanotube and in the framework of the density matrix formalism, shows that such self-cooling is possible down to a level where the average occupation number of the lowest flexural vibration mode of the nanowire is $\sim 0.1$.