Strong correlation effects in diatomic molecular electronic devices

TL;DR

This paper models how strong electron interactions in diatomic molecules attached to spin-polarized contacts affect conductance, especially during bond breaking, revealing suppressed transmission and new resonances.

Contribution

It introduces a Hubbard model for molecular conductance considering electron interactions and spin polarization, highlighting effects during bond dissociation.

Findings

Strong electron repulsion suppresses transmission upon dissociation.

Spin-polarized contacts induce coupling between molecular states.

Additional resonances reduce energy separation between conductance peaks.

Abstract

We present a qualitative model for a fundamental process in molecular electronics: the change in conductance upon bond breaking. In our model a diatomic molecule is attached to spin-polarized contacts. Employing a Hubbard Hamiltonian, electron interaction is neglected in the contacts and explicitly considered in the molecule, enabling us to study the impact of electron interaction on the molecular conductance. In the limit where the electron repulsion is strong compared to the binding energy (as it becomes the case upon dissociation) electron transmission in strongly suppressed compared to the non-interacting case. However, the spin-polarized nature of the contacts introduces a coupling between the molecular singlet and triplet states. This coupling in turn yields additional resonances in the transmission probability that significantly reduce the energetic separation appear between resonances. The ramifications of our results on transport experiments performed on nanowires with inclusions $H_2$ are discussed.