Seminaria Instytutowe

Analysis and control of electron dynamics, the birth of atto-magnetism and the predictive power of time-dependent DFT

by E.K.U. Gross (The Hebrew University Jerusalem)


This lecture is about the motion of electrons on the femto- and atto-second time scale; how it can be monitored, analyzed and, ultimately, controlled with ultra-short laser pulses. Real-time simulations are performed employing the ab-initio approach of time-dependent density functional theory (TDDFT) as theoretical tool. We shall visualize the laser-induced formation and breaking of chemical bonds in real time, and we shall highlight non-steady-state features of the electronic current through nano-scale junctions. With the goal of pushing magnetic storage processes towards faster and faster time scales, we have predicted that in many materials the local magnetic moment can be manipulated with ultrafast laser pulses on the femto- and even atto-second time scale. The underlying mechanism is an optically induced spin transfer (OISTR) from one magnetic sub-lattice to another. As an all-optical process, OISTR is temporally limited by the duration of the laser pulse, which may be as short as atto-seconds. OISTR was first predicted by real-time simulations and later confirmed experimentally. On longer time scales, decoherence arises from the non-adiabatic coupling of electronic and nuclear motion. A full ab-initio description of decoherence is achieved with algorithms deduced from an exact factorization of the full electron-nuclear wave function.