Carbon nanotube sensor for vibrating molecules

TL;DR

This paper investigates how a carbon nanotube sensor can detect vibrating molecules by analyzing transport properties influenced by vibrational modes, enabling molecule position and vibrational level characterization.

Contribution

It introduces a method to use transport measurements in CNT sensors to determine molecular position and vibrational energy levels through thermopower analysis.

Findings

Transport properties are dominated by position-dependent Franck-Condon factors.

Thermopower can reveal vibrational level spacing.

Transport measurements can infer molecular position along the CNT.

Abstract

The transport properties of a CNT capacitively coupled to a molecule vibrating along one of its librational modes are studied and its transport properties analyzed in the presence of an STM tip. We evaluate the linear charge and thermal conductances of the system and its thermopower. They are dominated by position-dependent Franck-Condon factors, governed by a position-dependent effective coupling constant peaked at the molecule position. Both conductance and thermopower allow to extract some information on the position of the molecule along the CNT. Crucially, however, thermopower sheds also light on the vibrational levelspacing, allowing to obtain a more complete characterization of the molecule even in the linear regime.