Replicas of the Kondo peak due to electron-vibration interaction in molecular transport properties

TL;DR

This paper theoretically investigates how electron-vibration interactions in molecular quantum dots lead to replica peaks of the Kondo resonance in conductance, revealing temperature-dependent behaviors aligned with experimental observations.

Contribution

It introduces a detailed theoretical model showing the emergence of vibrational side peaks in the Kondo regime and their temperature evolution, extending understanding of molecular transport phenomena.

Findings

Vibrational side peaks appear at multiples of vibronic energy in differential conductance.

Temperature evolution of satellite peaks mirrors the Kondo peak when vibronic energy is much larger than Kondo temperature.

The validity of this behavior diminishes when vibronic energy is comparable to the Kondo temperature.

Abstract

The low temperature properties of single level molecular quantum dots including both, electron-electron and electron-vibration interactions, are theoretically investigated. The calculated differential conductance in the Kondo regime exhibits not only the zero bias anomaly but also side peaks located at bias voltages which coincide with multiples of the energy of vibronic mode $V \sim \hbar\Omega/e$. We obtain that the evolution with temperature of the two main satellite conductance peaks follows the corresponding one of the Kondo peak when $\hbar\Omega \gg k_B T_K$, being $ T_K$ the Kondo temperature, in agreement with recent transport measurements in molecular junctions. However, we find that this is no longer valid when $ \hbar\Omega$ is of the order of a few times $k_B T_K$.