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SYEC: Symposium Exact-exchange and hybrid functionals meet quasiparticle energy calculations

SYEC 1: Exact-exchange and hybrid functionals meet quasiparticle energy calculations I

SYEC 1.6: Hauptvortrag

Donnerstag, 28. Februar 2008, 12:00–12:30, A 151

Ab-initio Many-Body Perturbation Theory of Electrons, Holes, Excitons, and their Dynamics — •Michael Rohlfing — Fachbereich Physik, Universität Osnabrück, Osnabrück, Germany

Excited electrons, holes, and correlated electron-hole pairs are of prime importance for the spectral properties of condensed matter. They are described by many-body perturbation theory (MBPT), which sytematically includes electronic exchange-correlation effects. The most common realization of this approach is Hedin’s GW approximation to the electron self-energy operator, combined with solving the Dyson equation of quasiparticles (electrons and holes) and the Bethe-Salpeter equation (BSE) of electron-hole pairs. This GW+BSE method has turned into a standard procedure for many systems, from bulk crystals to defects, surfaces, polymers, molecules, and adsorbate systems.

We will present the GW+BSE method and its relation to other approaches and discuss a number of prototypical systems and results. Particular emphasis will be put on the dynamics related to electronic excitations. On the one hand, the excited state on its own may be subject to femtosecond dynamics of the electronic degrees of freedom. On the other hand, the dependence of the total energy on the geometry may be different in the excited state, causing structural relaxation, spectral broadening, and Stokes shifts. In particular, we discuss prototypical excitations at surfaces, like charge-transfer processes at molecules on insulators [CO:MgO(001)] and particle expulsion from insulator surfaces [KI(001)] and semiconductor surfaces [H:Si(001)].