Relation between inelastic electron tunneling and vibrational excitation of single adsorbates on metal surfaces

TL;DR

This paper theoretically investigates how vibrational excitations of single adsorbates on metal surfaces relate to inelastic electron tunneling currents in STM, emphasizing the effects of vibrational lifetime and temperature on adsorbate motion.

Contribution

It provides a detailed analysis of the connection between vibrational generation rates and inelastic tunneling, including the impact of finite vibrational lifetimes and temperature broadening effects.

Findings

Vibrational excitation rates deviate from simple power-law near the IET threshold.

Temperature broadening is confined within a narrow voltage region around the threshold.

Vibrational lifetime broadening affects a wider voltage range below the IET threshold.

Abstract

We analyse theoretically a relation between the vibrational generation rate of a single adsorbate by tunneling electrons and the inelastic tunneling (IET) current in scanning tunneling microscope, and the influence of the vibrational excitations on the rate of adsorbate motions. Special attention is paid to the effects of finite lifetime of the vibrational excitations. We show that in the vicinity and below the IET threshold the rate of adsorbate motion deviates from a simple power-law dependence on the bias voltage due to the effects of bath temperature and adsorbate vibrational lifetime broadenings. The temperature broadening appears to be confined near the threshold voltage within a narrow region of several $k_B T$, whereas the lifetime broadening manifests itself in a much wider region of applied voltages below the IET threshold.