Electron-vibron coupling in suspended nanotubes

TL;DR

This paper investigates the electron-vibron coupling mechanisms in suspended nanotube quantum dots, focusing on how transverse and longitudinal fields influence the excitation of vibrational modes, with implications for experimental observations.

Contribution

It models the coupling mechanism considering both longitudinal and transverse fields, revealing the transverse field's potential to produce observable effects, but also highlighting discrepancies with recent experimental data.

Findings

Longitudinal field effects are too small to detect experimentally.

Transverse fields can induce significant Franck-Condon factors.

The length dependence of the coupling does not match recent experimental results.

Abstract

We consider the electron-vibron coupling in suspended nanotube quantum dots. Modelling the tube as an elastic medium, we study the possible coupling mechanism for exciting the stretching mode in a single-electron-transistor setup. Both the forces due to the longitudinal and the transverse fields are included. The effect of the longitudinal field is found to be too small to be seen in experiment. In contrast, the transverse field which couple to the stretching mode via the bending of the tube can in some cases give sizeable Franck-Condon factors. However, the length dependence is not compatible with recent experiments [Sapmaz et al. cond-mat/0508270].