# A coherent nanomechanical oscillator driven by single-electron tunnelling

## TL;DR

This paper demonstrates that a single-electron transistor integrated with a nanomechanical resonator can produce coherent mechanical oscillations, exhibiting laser-like properties such as coherence, injection locking, and frequency narrowing.

## Contribution

It provides experimental verification that strong electron tunnelling coupling can induce self-sustaining coherent mechanical oscillations in a nanomechanical system.

## Key findings

- Confirmed coherent oscillations in a carbon nanotube transistor system.
- Observed laser-like behaviors including injection locking.
- Demonstrated frequency narrowing through feedback mechanisms.

## Abstract

A single-electron transistor incorporated as part of a nanomechanical resonator represents an extreme limit of electron-phonon coupling. While it allows for fast and sensitive electromechanical measurements, it also introduces backaction forces from electron tunnelling which randomly perturb the mechanical state. Despite the stochastic nature of this backaction, under conditions of strong coupling it is predicted to create self-sustaining coherent mechanical oscillations. Here, we verify this prediction using time-resolved measurements of a vibrating carbon nanotube transistor. This electromechanical oscillator has intriguing similarities with a laser. The single-electron transistor, pumped by an electrical bias, acts as a gain medium while the resonator acts as a phonon cavity. Despite the unconventional operating principle, which does not involve stimulated emission, we confirm that the output is coherent, and demonstrate other laser behaviour including injection locking and frequency narrowing through feedback.