Spin transport in higher n-acene molecules

Abstract

We investigate the spin-transport properties of molecules belonging to the acenes series by using density functional theory combined with the nonequilibrium Green's function approach to electronic transport. While short acenes are found to be nonmagnetic, molecules comprising more than nine acene rings have a spin-polarized ground state. In their gas phase, these have a singlet total spin configuration, where the two unpaired electrons occupy the doubly degenerate highest molecular orbital. Such an orbital degeneracy is however lifted once the molecule is attached asymmetrically to Au electrodes via thiol linkers, leading to a net 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.