Incoherent dynamics of vibrating single-molecule transistors

TL;DR

This paper models the tunneling conductance of vibrating single-molecule transistors, showing that electrostatic effects can induce negative differential conductance and highlighting the quantum nature of oscillator transitions.

Contribution

It provides a quantitative analysis of the dynamics in vibrating single-molecule transistors, emphasizing the influence of electrostatics on quantum oscillator behavior and conductance features.

Findings

Calculated I-V curves match experimental features

Electrostatic potential strongly influences oscillator dynamics

Negative differential conductance can occur due to bias-controlled quantum transitions

Abstract

We study the tunneling conductance of nano-scale quantum ``shuttles'' in connection with a recent experiment (H. Park et al., Nature, 407, 57 (2000)) in which a vibrating C^60 molecule was apparently functioning as the island of a single electron transistor (SET). While our calculation starts from the same model of previous work (D. Boese and H. Schoeller, Europhys. Lett. 54, 66(2001)) we obtain quantitatively different dynamics. Calculated I-V curves exhibit most features present in experimental data with a physically reasonable parameter set, and point to a strong dependence of the oscillator's potential on the electrostatics of the island region. We propose that in a regime where the electric field due to the bias voltage itself affects island position, a "catastrophic" negative differential conductance (NDC) may be realized. This effect is directly attributable to the magnitude of overlap of final and initial quantum oscillator states, and as such represents experimental control over quantum transitions of the oscillator via the macroscopically controllable bias voltage.