Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Electron and spin dynamics

O 8.6: Talk

Monday, March 26, 2012, 11:45–12:00, A 060

The role of intermediate states in two-photon photoemission from Si(001) — •Henning Husser and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, Germany

Two-photon photoemission (2PPE) spectra contain detailed information about the unoccupied states [1], and time resolved 2PPE can reveal the dynamics. We have developed a non-perturbational approach to calculate photocurrents by time-dependent simulations and applied it to the calculation of normal-emission photocurrents from Si(001). Here we focus on the analysis of 2PPE Si(001) normal emission spectra from the simulations in the light of the expression known from perturbation theory. The intermediate states occurring in this expression are linked to both the initial state and to the final state by matrix elements. Intermediate states can become prominent in the spectra if they couple strongly to the initial states or the final states. Variation of the polarization of the light wave can be used to tune the matrix elements via the respective selection rules. Resonances in the emission intensity for a fixed initial state as a function of photon energy can be assigned to intermediate states. This will be used to derive information about the intermediate states in case of normal-emission 2PPE from Si(001). In particular the role of surface resonances, as reported by Fauster et al. [2], will be investigated.

[1] W. Schattke et al., Phys. Rev. B 78, 15534 (2008).

[2] T. Fauster et al., Verhandl. DPG (VI) 46, 1/490 (2011).