Analysis and control of electron dynamics: An ab-initio perspective on the femto-second time scale

Abstract. This lecture is about the motion of electrons, how it can be monitored, analyzed and, ultimately, controlled with external fields on the femto-second time scale. The investigations are performed with ab-initio simulations, using time-dependent density functional theory as theoretical tool. We shall visualize the laser-induced formation and breaking of chemical bonds in real time, and we shall adress questions like: How much time needs an electron to complete a transition from one state to another? Another main topic will be quantum transport. Time-dependent features of the electronic current through nano-scale junctions will be studied for electron pumps and molecular optical switches. A combination of quantum optimal control theory with time-dependent density functional theory will be presented as a method to compute laser pulses that are optimised to achieve a given goal. As an example, we shall calculate the laser pulse needed to switch the chirality of currents in quantum rings. Finally we will study the ultrafast laser induced demagnetisation of ferromagnetic solids.