STEADY-STATE DENSITY FUNCTIONAL THEORY FOR NON-EQUILIBRIUM QUANTUM SYSTEMS

Abstract

We study the electronic and transport properties of a molecular junction under finite bias. First, based on Hershfield's non-equilibrium statistics, we developed a steady state density functional theory (SS-DFT) and showed that two electron densities, current-carrying electron density and equilibrium electron density, determine the properties of the molecular junction in steady state. Second, based on the stationary condition of an effective ground state energy, we derived a dual mean field (DMF) approach for obtaining the desired steady state. In the DMF approach, current-carrying and equilibrium electrons experience different mean field potentials and two sets of coupled mean field equations need to be solved simultaneously. Third, we generalized the Thomas-Fermi-Dirac model into non-equilibrium situation and obtained the exchange energy functional with non-equilibrium correction. Finally, we have implemented SS-DFT in SIESTA package and simulated several realistic molecular junctions. Our study paves the way to first-principles methods for the study of molecular junctions under finite bias.