Status and challenges of time dependent transport through nanostructures

The quantum coherent AC transport is found to be mediated by resonant states extending the entire molecule, or mediated by localized states within the molecule. The theoretical analysis shows that a critical control of conductance of short molecules can achieved by a finite frequency AC bias. The transport properties of molecular devices under a high frequency AC bias is a difficult problem of quantum transport theory, and a first principles self-consistent analysis of finite frequency AC conductance for the Metal-Molecule-Metal device configuration. For atomistic analysis of the transport property through Metal-Molecule-Metal device, the NEGF-DFT formalism is used. In this ab initio technique and LCAO formalism is used, where density functional theory (DFT) is carried out within the Keldysh nonequilibrium Green´s function (NEGF) formalism. From both theory and application point of views, another important issue which has yet to be resolved is to predict how fast or how slow a nanoelectronic device can turn on/off a current from quantum mechanical first principles