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Project B.1.4

Charge transfer and screening on surfaces

The goal of this project is to gain understanding of (i) the dynamics of ultrafast charge transfer between chemisorbed particles and their substrates, (ii) state-resolved electron transport dynamics in solids through interfaces, (iii) transition from ballistic to collective electron motion, screening and band-structure build-up dynamics. Understanding of all these processes is important for many fields like molecular electronics, photovoltaics, electronically stimulated materials modification and spectroscopy. A pioneering proofof-concept study in this field has been reported.

Just as in Project B.1.3, our spectroscopic methods of choice will be few-femtosecond-UV-pump / attosecond-XUV-probe spectroscopy and triggering processes with attosecond XUV pulses and interrogating the unfolding dynamics by capturing outgoing (primary / secondary) electrons by means of as-streaking schemes to answer these questions. The experiments will be performed in the attosecond UHV beamline AS-3 equipped with dispersive and TOF electron analysers, as well as angular and spin detection. Concomitant measurements employing synchrotron radiation will provide a complementary perspective and allow a comparison with attosecond electron dynamics examined by means of the core-hole-clock technique.

Time-dependent density functional theory in the time domain will be used to simulate the charge transfer dynamics and interpret the experiments. Theory of electronic excitation and transport in the solid on the sub-femtoscecond time-scale will be described as spatial and temporal defects embedded in bandstructure descriptions. Wave-packet methods will be employed to understand formation and coherent propagation of electronic excitations through interfaces and surfaces. Furthermore the cooperations with the groups of P. Echenique (DIPC, San Sebastian, cf. [B1.28]), M. Wolf (FHI Berlin) and J. P. Gauyacq (Paris) will be continued.