Nano-mechanics driven by Andreev tunneling

TL;DR

This paper predicts that a nanoelectromechanical system with a carbon nanotube and superconducting leads can exhibit mechanical instability and self-sustained oscillations driven by Andreev tunneling, affecting electric current.

Contribution

It introduces a theoretical analysis of mechanically unstable behavior induced by Andreev tunneling in a CNT-based nanoelectromechanical system, highlighting control parameters.

Findings

Mechanical instability leads to self-sustained oscillations.

Oscillations suppress the DC electric current.

Behavior is controlled by Josephson phase and electron energy levels.

Abstract

We predict and analyze mechanical instability and corresponding self-sustained mechanical oscillations occurring in a nanoelectromechanical system composed of a metallic carbon nanotube (CNT) suspended between two superconducting leads and coupled to a scanning tunneling microscope (STM) tip. We show that such phenomena are realized in the presence of both the coherent Andreev tunneling between the CNT and superconducting leads, and an incoherent single electron tunneling between the voltage biased STM tip and CNT. Treating the CNT as a single-level quantum dot, we demonstrate that the mechanical instability is controlled by the Josephson phase difference, relative position of the electron energy level, and the direction of the charge flow. It is found numerically that the emergence of the self-sustained oscillations leads to a substantial suppression of DC electric current.