报告题目：Steady-State Density Functional Theory: From Fundamental to
We present a steady-state density functional theory (SS-DFT) for modeling electronic and transport properties of nonequilibrium quantum systems such as molecular junctions under a finite bias. Based on nonequilibrium quantum statistics, we show that given two electron densities, the total electron density (ρt) and the density of current-carrying electrons (ρn), the steady-state properties of a nonequilibrium quantum system can be uniquely determined. A direct consequence of the theory is that the ground-state density functional theory (GS-DFT) based approach is in principle not correct for steady-state nonequilibrium systems. A dual mean-field (DMF) approach that is applicable to realistic quantum systems is then derived. The key idea of the DMF approach is that the current-carrying electrons ‘feel’ a different mean-field potential from equilibrium electrons that do not contribute to electric current. The SS-DFT and DMF approach have been applied to various kinds of molecular scale junctions. Electronic structures and I-V characteristics from SS-DFT are compared with those obtained from the conventional GS-DFT based transport approach. If time permitting, we will also discuss one example to show how SS-DFT can be used to explain puzzling experimental observations.
报告人简历：Dr. Chun Zhang earned his PhD in physics from University of Florida in 2004. After 3 years of postdoc research experiences in Georgia Institute of Technology, he took a faculty job in National University of Singapore (NUS). He now is associate professor in Department of Physics and also Chemistry at NUS. Dr. Zhang's research is mainly focused on theoretical/computational modelling of materials at various scales ranging from small molecules to bulk systems. His current interests include molecular electronics/spintronics and surface physics/chemistry. In total, Dr. Zhang has published 60+ papers with 2610+ citations.