Symmetry-induced interference effects in metalloporphyrin wires

TL;DR

This study investigates how symmetry and strong electronic correlations influence quantum interference and transport in metalloporphyrin wires, highlighting the importance of accurate correlation treatment for nanoscale device design.

Contribution

It demonstrates the role of symmetry-dependent d state coupling and the impact of strong correlations on conductance and spin-filtering in metalloporphyrins, using DFT and DFT+U methods.

Findings

Interference effects produce Fano resonances depending on d state symmetry.

Including U opens a gap affecting conductance and spin-filtering.

Proper correlation treatment is essential for accurate transport predictions.

Abstract

Organo-metallic molecular structures where a single metallic atom is embedded in the organic backbone are ideal systems to study the effect of strong correlations on their electronic structure. In this work we calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched by gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT+U approaches. The zero bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes qualitatively the conductance and spin-filtering behavior in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets.