Atomic Motion in Single H$_{2}$ and D$_{2}$ Molecule Junction Induced by Phonon Excitation

TL;DR

This study explores how phonon excitation induces atomic motion in single H₂ and D₂ molecule junctions with gold electrodes, revealing differences in structural changes due to vibrational energy.

Contribution

It demonstrates that phonon-induced structural changes occur only in Au/H₂/Au junctions, highlighting the role of vibrational zero-point energy differences.

Findings

Symmetric peaks in dI/dV spectra for Au/H₂/Au junctions

No such peaks observed for Au/D₂/Au junctions

Structural change driven by phonon excitation only in H₂ junctions

Abstract

We have investigated Au atomic contacts in H$_{2}$ and D$_{2}$ environment by conductance measurement and $dI/dV$ spectroscopy. A single H$_{2}$ or D$_{2}$ molecule was found to bridge Au electrodes. In the case of the Au/H$_{2}$/Au junction, symmetric peaks were observed in $dI/dV$ spectra, while they were not observed for the Au/D$_{2}$/Au junction. The shape of the peaks in $dI/dV$ spectra originated from the structural change of the single molecule junction induced by the phonon excitation. The structural change could occur only for the Au/H$_{2}$/Au junction. The difference in the two single molecule junctions could be explained by larger zero point energy of Au-H$_{2}$ vibration mode than that in the Au/H$_{2}$/Au junction.