Theoretical treatment of finite and extended electronic systems

J. Berakdar, N. Fomynikh, A. Ernst

A variety of material properties are dictated by the motion of the electrons. For example optical, chemical and magnetic properties depend of the electronic structure in a decisive way. On the other hand a theoretical description of all the facets of the excitation spectrum of a many-body electronic system is still out of reach.
The difficulties encountered are practical as well as conceptual ones:

The traditional approach towards the many-body problem has been to reduces it to a tractable single particle one in an effective (non-local) field created by the rest of the system. This single-particle concept proved very useful for explaining a variety of phenomena. However, a number of questions are still open as which extent such an effective field treatment is capable of explaining processes that are dependent of the local electronic correlation.

In this project we develop conceptual and numerical methods to dealing with correlated systems. Our prime focus is the excitation spectrum of few and many-body systems, such as atomic complexes and surfaces.
Our methods are based on the Green function approach (perturbation theory, GW method,...), Faddeev equations, and on effective field methods, such as density functional theory.

Collaborations:
J. Kudronovsky (Prague)
A.Dorn, R. Moshhammer, and J. Ullrich (Freiburg)
A. Lahmam-Bennani (Paris)