PROJECTS

Electronic structure and excitation spectra of magnetic materials within first-principles many-body perturbation theory

PRINCIPAL INVESTIGATOR

Dr. Arno Schindlmayr Forschungszentrum Jülich GmbH Institut für Festkörperforschung D-52425 Jülich Germany +49 2461 61 4210 +49 2461 61 2850 a.schindlmayr@fz-juelich.de

TOGETHER WITH

Dr. Gustav Bihlmayer Forschungszentrum Jülich GmbH Institut für Festkörperforschung D-52425 Jülich Germany +49 2461 61 4677 +49 2461 61 2620 G.Bihlmayer@fz-juelich.de

Prof. Dr. Stefan Blügel Forschungszentrum Jülich GmbH Institut für Festkörperforschung D-52425 Jülich Germany +49 2461 61 4249 +49 2461 61 2620 S.Bluegel@fz-juelich.de

ABSTRACT

We develop a computational method based on many-body perturbation theory to enable first-principles calculations of the electronic structure and excitation spectra of magnetic materials. To this effect we extend the GW approximation for the electronic self-energy to take the spin polarisation of the electron system into account. At this level the self-energy is still calculated separately for each spin channel. As a major goal, we then treat possible spin-flip processes by including appropriate vertex corrections in the form of a scattering matrix that couples the two spin channels. The implementation is based on an all-electron approach and avoids the use of pseudopotentials. Key quantities that can be obtained with this method are the quasiparticle band structure, including the exchange splitting between the two spin channels, as well as the spectral function, which in addition to the main quasi-particle peaks also shows additional collective excitations in the form of satellite resonances. The lifetime of the excitations can be obtained from the imaginary part of the complex quasi-particle energies. The theoretical approach is universal and can be applied to magnetic bulk materials, surfaces and nanostructures if spin polarisation plays an important role.