Molecule-electrode connection mode determines whether VR radical can act as a spin filter: A first principles study

Abstract

The ability of organic radicals to maintain their open-shell feature in the device environment directly determines whether they can act as spin filters. Based on the recently synthesized stable VR-1 radical, we have designed two molecular devices with symmetric and asymmetric molecule-electrode connections and investiaged their spin-polarized transport properties using density functional theory and non-equilibrium Green's function methodology. The results show that the presence of unpaired electron in VR-1 radical is not a sole requirement for causing spin polarization and the molecular-electrode connection mode plays a decisive role in the transport characteristics. VR-1 can be used as a spin filter in the asymmetric connection mode, while it loses its open-shell feature in the symmetric connection mode. Moreover, VR-1 with the asymmetric connection mode exhibits obvious spin-rectifying effect. The results are analyzed by the spin-resolved frontier molecular orbitals and eigenstates, Mulliken population analysis, transmission spectra and transmission eigenstates.