Ultrastrong coupling between electron tunneling and mechanical motion

TL;DR

This paper reports the measurement and modeling of ultrastrong coupling between single-electron tunneling and nanomechanical motion in a suspended carbon nanotube, achieving the highest coupling ratio among electromechanical systems.

Contribution

The study demonstrates the first measurement of ultrastrong coupling in a suspended carbon nanotube device, revealing the highest coupling ratio to date and suggesting potential for further improvements.

Findings

Achieved a coupling ratio of 2.72, the highest among electromechanical systems.

Measured a coupling strength of approximately 0.80 GHz.

Identified potential for even higher coupling ratios with device improvements.

Abstract

The ultrastrong coupling of single-electron tunneling and nanomechanical motion opens exciting opportunities to explore fundamental questions and develop new platforms for quantum technologies. We have measured and modeled this electromechanical coupling in a fully-suspended carbon nanotube device and report a ratio of $g_\mathrm{m}/\omega_\mathrm{m} = 2.72 \pm 0.14$, where $g_\mathrm{m}/2\pi = 0.80\pm 0.04$ GHz is the coupling strength and $\omega_\mathrm{m}/2\pi=294.5$ MHz is the mechanical resonance frequency. This is well within the ultrastrong coupling regime and the highest among all other electromechanical platforms. We show that, although this regime was present in similar fully-suspended carbon nanotube devices, it went unnoticed. Even higher ratios could be achieved with improvement on device design.