Regensburg 2002 – scientific programme

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O: Oberflächenphysik

O 13: Postersitzung (Adsorption an Oberfl
ächen, Elektronische Struktur, Magnetismus in reduzierten Dimensionen, Epitaxie und Wachstum, Halbleiteroberfl
ächen und -grenzfl
ächen, Organische Dünnschichten)

O 13.25: Poster

Monday, March 11, 2002, 18:00–21:00, Bereich C

Quasiparticle band structure and optical spectrum of the LiF(001) surface — •Neng-Ping Wang, Michael Rohlfing, Peter Krüger, and Johannes Pollmann — Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster

This work deals with the quasiparticle band structure and optical excitation of the LiF(001) surface. First, we calculate the ground state geometry of the surface using density-functional theory within the local-density approximation (LDA). Then, applying the GW approximation for the self-energy, we calculate the quasiparticle band structure. For the dielectric screening, both the random-phase approximation and a model dielectric function are used, both giving essentially the same results. The obtained energy gap for the surface is found to be 6 eV larger than the LDA energy gap. We have also found a considerable surface core-level shift of the Li 1s state. Finally, we take into account the electron-hole interaction and solve the Bethe-Salpeter equation for the two-particle Green’s function. This allows us to investigate the optical absorption spectrum. The calculated spectrum of bulk LiF, which is dominated by a strong exciton peak at 12.5 eV, is in very good agreement with experiment. Calculations for excitonic effects at the LiF surface are in progress.