Spin transport in higher n-acene molecules

TL;DR

This study explores spin transport in acene molecules, revealing that longer acenes become spin-polarized and can serve as effective spin-filters when attached to gold electrodes, advancing organic spintronics.

Contribution

It demonstrates the spin-polarized ground state in longer acenes and their potential as spin-filters in molecular electronics, using DFT and NEGF methods.

Findings

Longer acenes (>9 rings) are spin-polarized.

Asymmetric attachment to Au induces fractional magnetic moments.

Long acenes can act as efficient spin-filters.

Abstract

We investigate the spin transport properties of molecules belonging to the acenes series by using density functional theory combined with the non-equilibrium Green's function approach to electronic transport. While short acenes are found to be non-magnetic, molecules comprising more than nine acene rings have a spin-polarized ground state. In their gas phase these have a singlet total spin configuration, since the two unpaired electrons occupying the doubly degenerate highest molecular orbital are antiferromagnetically coupled to each other. Such an orbital degeneracy is however lifted once the molecule is attached asymmetrically to Au electrodes via thiol linkers, leading to a fractional magnetic moment. In this situation the system Au/n-acene/Au can act as an efficient spin-filter with interesting applications in the emerging field of organic spintronics.