Spin splitter and spin filter in a three terminals device under Zeeman effect in a tight binding approach

Abstract

In this work we propose a theoretical study of impurities effects in charge transport through a linear and an aromatic three terminals device under an external magnetic field. We use the Landauer approach, with the electronic structure treated at tight binding (TB) level and model the self-energy with the wide band limit approximation. For the linear chain, we use decimation techniques to renormalize the system, reducing it into a 3 × 3 matrix, so as to make an analytical treatment. For aromatic systems we opt for numerical calculations. Our main results suggest that no matter the system, by introducing impurities into the chain together with an applied magnetic field, there is a possibility to have filter spin (through the system) or splitter spins (on each branch), due to the Zeeman effect. The results agree with other theoretical works for systems with also intrinsic asymmetry of the device but caused by the different polarization into distinct branches. Also, our theoretical approach reveals, in a clear way, how the impurity on each branch makes the system behaves like a spin filter or a spin splitter, depending on the onsite energies of the impurities.