Inelastic electron tunneling via molecular vibrations in single-molecule transistors

TL;DR

This paper demonstrates inelastic electron tunneling spectroscopy of single molecules in transistors, revealing vibrational excitations and their modulation by electronic states, including Kondo effects, with in-situ tunability.

Contribution

It introduces a method to study vibrational modes in single-molecule transistors using inelastic cotunneling, showing how vibrational features evolve with electronic tuning.

Findings

Vibrational excitations match Raman and infrared spectra.

Vibrational features shift with electronic resonance tuning.

Vibrational satellites observed around Kondo resonance.

Abstract

In single-molecule transistors, we observe inelastic cotunneling features that correspond energetically to vibrational excitations of the molecule, as determined by Raman and infrared spectroscopy. This is a form of inelastic electron tunneling spectroscopy of single molecules, with the transistor geometry allowing in-situ tuning of the electronic states via a gate electrode. The vibrational features shift and change shape as the electronic levels are tuned near resonance, indicating significant modification of the vibrational states. When the molecule contains an unpaired electron, we also observe vibrational satellite features around the Kondo resonance.