Torsional oscillation of carbon nanotubes driven by electron spins

TL;DR

This paper presents a theoretical study of how electron spins can induce torsional vibrations in a suspended carbon nanotube quantum dot, revealing a spin-driven mechanism for nanoelectromechanical actuation.

Contribution

It introduces a novel spin-rotation coupling mechanism enabling current-controlled torsional vibrations in carbon nanotubes, supported by a detailed theoretical analysis.

Findings

Resonant current behavior when Zeeman splitting matches phonon energy

Significant increase in phonon population at resonance

Potential for detectable torsional vibrations driven by electron spins

Abstract

We theoretically investigate the current-induced excitation of torsional vibrations in a suspended carbon nanotube (CNT) quantum dot. By considering a CNT clamped between half-metallic ferromagnetic electrodes with an antiparallel magnetization configuration, we demonstrate that the spin-rotation coupling enables the transfer of angular momentum from electron spins to the mechanical torsional mode under a constant source-drain voltage. Using a master-equation approach to analyze the coupled dynamics of the dot levels and a quantized torsional oscillator, we evaluate the steady-state current and phonon distribution. We find that when the Zeeman splitting matches the torsional phonon energy, the system exhibits a sharp resonant behavior in the current, accompanied by a significant increase in the phonon population. Our estimates for realistic device parameters indicate that this spin-driven mechanism can drive CNT torsional vibrations with detectable amplitudes. This work provides a theoretical basis for current-controlled actuation of nanoelectromechanical systems via the spin angular momentum of electrons.