Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 43: Theory of electronic structure

HL 43.2: Talk

Thursday, March 29, 2007, 14:15–14:30, H14

Excitonic Effects in MnO: An Application of Spin-Polarized BSE — •Claudia Rödl, Frank Fuchs, Jürgen Furthmüller, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

As it is desirable to calculate optical spectra also for magnetic materials we approach the problem of evaluating excitation properties for collinear spin-polarized systems within the Bethe-Salpeter equation (BSE). As an interesting test material we choose the antiferromagnetic insulator MnO.

We start with a calculation of the electronic ground state in the framework of density-functional theory (DFT) within the generalized-gradient approximation (GGA) and use the projector-augmented wave (PAW) method to describe the wave functions. In the case of MnO the main problem consists in obtaining reasonable quasiparticle energies. We compute quasiparticle shifts using Hedin’s GW approximation in a model scheme.

To treat magnetic materials one has to extend the usual BSE scheme in order to describe the spin degree of freedom. As a consequence the rank of the BSE Hamiltonian doubles resulting in increased computational cost. The optical spectra are determined by solving an initial-value problem instead of a direct diagonalization of the Hamiltonian.