Electron-vibration interaction in transport through atomic gold wires

TL;DR

This paper investigates how electron-vibration interactions affect electrical conductance in atomic gold wires, using theoretical calculations to explain experimental observations of conductance drops at vibrational energies.

Contribution

The study provides a detailed theoretical analysis of electron-vibration effects in gold atomic wires, including mode broadening and geometry-dependent signatures, aligning well with experimental data.

Findings

Small conductance drops occur at vibrational energies.

Multiple vibrational modes can cause several conductance drops.

Mode broadening explains the single wide conductance drop in experiments.

Abstract

We calculate the effect of electron-vibration coupling on conduction through atomic gold wires, which was measured in the experiments of Agra\"it et al. [Phys. Rev. Lett. 88, 216803 (2002)]. The vibrational modes, the coupling constants, and the inelastic transport are all calculated using a tight-binding parametrization and the non-equilibrium Green function formalism. The electron-vibration coupling gives rise to small drops in the conductance at voltages corresponding to energies of some of the vibrational modes. We study systematically how the position and height of these steps vary as a linear wire is stretched and more atoms are added to it, and find a good agreement with the experiments. We also consider two different types of geometries, which are found to yield qualitatively similar results. In contrast to previous calculations, we find that typically there are several close-lying drops due to different longitudinal modes. In the experiments, only a single drop is usually visible, but its width is too large to be accounted for by temperature. Therefore, to explain the experimental results, we find it necessary to introduce a finite broadening to the vibrational modes, which makes the separate drops merge into a single, wide one. In addition, we predict how the signatures of vibrational modes in the conductance curves differ between linear and zigzag-type wires.