Non-equilibrium vertex correction: disorder scattering in magnetic tunnel junctions

We report a first principles formalism and its numerical implementation for treating quantum transport properties of nanoelectronic devices with atomistic disorder. We developed a nonequilibrium vertex correction (NVC) theory to handle the configurational average of random disorder at the density matrix level so that disorder effects to nonlinear and nonequilibrium quantum transport can be calculated from atomic first principles in a self-consistent and efficient manner. We implemented the NVC into a Keldysh non-equilibrium Green's function (NEGF) based density functional theory (DFT) and applied the NEGF-DFT-NVC formalism to magnetic tunnel junctions with interface roughness disorder. Our results show that disorder has dramatic effects to nonlinear spin injection and tunnel magneto-resistance ratio.