Regensburg 2025 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

TT: Fachverband Tiefe Temperaturen

TT 17: Correlated Electrons: Method Development

TT 17.1: Talk

Tuesday, March 18, 2025, 09:30–09:45, H33

Accuracy of embedded impurity methods for spin-polarized systems — •Kevin Ackermann and Maurits W. Haverkort — Institute for Theoretical Physics, Heidelberg, Germany

Ab-Initio embedded impurity approaches, such as DFT+DMFT, have proven to be a robust tool in understanding physical properties of materials for quite some time. Still the intersection between the employed mean field method, like Hartree-Fock or DFT, and the many-body impurity remains awkward. One of the issues can be exemplified for spin-polarised systems. For these materials spin is no longer a good quantum number in mean-field approximations and SU(2)-symmetry is explicitly broken by the usual spin-polarized mean-field methods. This automatically turns every spin-flip excitation into a Hund’s coupling excitation, distorting the many-body spectral function in the process. Standard methods used in quantum chemistry to remedy this, such as restricted open shell Hartree-Fock/Kohn-Sham, average over the different spin potentials or densities. However, there are many flavors of realizing the needed spin averaging. To examine the impact of this choice, we compare ground state properties, such as bond lengths, as well as excitation spectra among a multitude of spin averaging schemes for a range of molecules.

Keywords: LDA+DMFT; Ab initio ligand field theory; Transition metal compounds; Molecular magnets; Correlated materials