Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 13: Theory of electronic structure

HL 13.3: Vortrag

Montag, 25. Februar 2008, 16:45–17:00, EW 202

An efficient approach to bound excitons: Applications to model and ab initio band structures. — •Frank Fuchs, Claudia Rödl, André Schleife, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik and European Theoretical Spectroscopy Facility (ETSF), Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743 Jena, Germany

The accurate calculation and parameter-free prediction of optical spectra including excitonic effects is highly desirable for both fundamental and applied research. Excitonic effects can be treated in the framework of many-body perturbation theory and the Bethe-Salpeter equation (BSE), by solving an eigenvalue problem for the electron-hole Hamiltonian Ĥ. Although an efficient method for the calculation of excitonic spectra in an extended frequency range is available [1], a comparably efficient approach to bound excitonic states or even dark excitons is lacking. Instead, the diagonalization of Ĥ, with computational costs scaling with the number of pair states N like O(N³), is required. Thus computational studies are usually limited to well behaved problems and/or are insufficiently converged with respect to N. We present a numerically efficient approach for the calculation of a limited number of excitonic states avoiding the full diagonalization of Ĥ. The approach is tested for its accuracy and performance by numerically solving the BSE for the Wannier-Mott two-band model in k-space and real semiconductors like InN and ZnO.

[1] W.G. Schmidt et al. , Phys. Rev. B 67, 085307 (2003).