Quantum transport through a deformable molecular transistor

TL;DR

This paper investigates how electron-electron and electron-phonon interactions influence quantum transport in a molecular transistor, revealing effects like conductance asymmetries and different Kondo regimes.

Contribution

It provides an analytical and numerical study of phonon effects on transport and Kondo phenomena in molecular transistors, highlighting qualitative differences between weak and strong coupling regimes.

Findings

Conductance shows asymmetry due to phonon modulation.

Kondo effect persists with electron-phonon interactions.

Perfect transmission occurs at odd electron counts regardless of interactions.

Abstract

The linear transport properties of a model molecular transistor with electron-electron and electron-phonon interactions were investigated analytically and numerically. The model takes into account phonon modulation of the electronic energy levels and of the tunnelling barrier between the molecule and the electrodes. When both effects are present they lead to asymmetries in the dependence of the conductance on gate voltage. The Kondo effect is observed in the presence of electron-phonon interactions. There are important qualitative differences between the cases of weak and strong coupling. In the first case the standard Kondo effect driven by spin fluctuations occurs. In the second case, it is driven by charge fluctuations. The Fermi-liquid relation between the spectral density of the molecule and its charge is altered by electron-phonon interactions. Remarkably, the relation between the zero-temperature conductance and the charge remains unchanged. Therefore, there is perfect transmission in all regimes whenever the average number of electrons in the molecule is an odd integer.