# Electronic Excitations & Spindynamics

## Correlation in electronic band structures & quasiparticles dynamics

Photoemission spectroscopy and the quasiparticle band structures derived from it are the most important sources of information about the electronic structure of solids. They characterize excitations of the electron system and often show strong signatures of correlation. In contrast to density-functional theory, many-body perturbation theory provides an exact framework for studying these excited states. Practical implementations are based on the *GW* approximation for the electronic self-energy, which yields band structures and the dynamics of quasiparticle excitations, including their finite lifetime, in close agreement with experiments.

The SPEX code is a practical implementation of the *GW* approximation within the FLAPW method, in which valence and core electrons are treated on the same footing. This highly accurate electron-structure method allows the description of a large variety of materials and physical effects.

(C. Friedrich, A. Gierlich)

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Spinwellen

Fast magnetic switches are a key ingredient for many modern technologies, such as computer hard disks with accelerated read/write cycles. The mediators of these magnetization processes are spin waves, which occur on a picosecond time scale. To study the material-specific spin-wave spectra and their dynamics, we employ advanced many-body techniques in combination with the Bethe-Salpeter equation. With parameters derived from these elementary processes, it is then possible to describe the magnetization of larger domains in technologically relevant devices.

(E. Sasioglu, C. Friedrich, A. Schindlmayr)