Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)

O 27.122: Poster

Dienstag, 24. März 2009, 18:30–21:00, P2

Non-perturbative approach to photoemission by direct simulation of photo-currents — •Henning Husser, Jan van Heys, and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, Germany

We present a non-perturbative ab initio approach for the calculation of photo-currents by direct simulation of the photoemission process. The electronic structure of the solid surface, which is initially in its electronic ground state, is calculated within density functional theory using a slab geometry. In a first approach, we integrate the time-dependent single-particle Kohn-Sham equations only for a frozen-in effective potential. The excitation by a fs laser-pulse is accounted for within the dipole approximation. Decoupling of the slabs is achieved by an optimized absorbing potential in the vacuum region. Inelastic scattering of the photo-excited electrons in the solid is roughly accounted for by an absorptive gauge-invariant (constructed in analogy to [1]) optical potential, which is acting only on the excited-state admixtures to the time-dependent wave-functions. The spectra are derived from the Fourier transform of the time-dependent wave-functions. The integration of the time-dependent single-particle equations is carried through with an extended [2] version of the fhimd code from the Fritz-Haber-Institut in Berlin. We present photoemission spectra for the Si(001) surface. We argue how the method can be extended to highly excited systems.

[1] S. Ismail-Beigi et al., Phys. Rev. Lett. 87, 087402 (2001).

[2] J. van Heys et al., Phase Transitions 78, 773 (2005).