Inelastic Scattering in Metal-H2-Metal Junctions

TL;DR

This paper uses first-principles calculations to analyze how electron-phonon interactions affect conductance in metal-H2-metal junctions, revealing mode-specific effects and comparing results with experiments.

Contribution

It provides a detailed first-principles analysis of inelastic scattering effects in metal-H2-metal junctions, highlighting the role of vibrational modes and electrode material.

Findings

Conductance decreases at vibrational excitation thresholds.

Transverse vibrations can enhance conductance in Pt junctions.

Au junctions show negligible effect from transverse modes.

Abstract

We present first-principles calculations of the dI/dV characteristics of an H2 molecule sandwiched between Au and Pt electrodes in the presence of electron-phonon interactions. The conductance is found to decrease by a few percentage at threshold voltages corresponding to the excitation energy of longitudinal vibrations of the H2 molecule. In the case of Pt electrodes, the transverse vibrations can mediate transport through otherwise non-transmitting Pt $d$-channels leading to an increase in the differential conductance even though the hydrogen junction is characterized predominately by a single almost fully open transport channel. In the case of Au, the transverse modes do not affect the dI/dV because the Au d-states are too far below the Fermi level. A simple explanation of the first-principles results is given using scattering theory. Finally, we compare and discuss our results in relation to experimental data.