Orbital Kondo effect in Cobalt-Benzene sandwich molecules

TL;DR

This paper investigates the orbital Kondo effect in a cobalt-benzene sandwich molecule connected to copper nanocontacts, revealing a unique temperature-dependent resonance due to electron correlations.

Contribution

It introduces a realistic model of correlated molecular transport showing the orbital Kondo effect arising from Co 3d shell interactions.

Findings

Orbital Kondo effect observed under slight compression of the molecule.

Presence of a sharp Abrikosov-Suhl resonance at the Fermi level.

Fano line shape in low bias conductance indicating Kondo physics.

Abstract

We study a Co-benzene sandwich molecule bridging the tips of a Cu nanocontact as a realistic model of correlated molecular transport. To this end we employ a recently developed method for calculating the correlated electronic structure and transport properties of nanoscopic conductors. When the molecule is slightly compressed by the tips of the nanocontact the dynamic correlations originating from the strongly interacting Co 3d shell give rise to an orbital Kondo effect while the usual spin Kondo effect is suppressed due to Hund's rule coupling. This non-trivial Kondo effect produces a sharp and temperature-dependent Abrikosov-Suhl resonance in the spectral function at the Fermi level and a corresponding Fano line shape in the low bias conductance.