Intershell interactions in correlated materials: A slave-rotor approach

The treatment of intershell interactions remains a major challenge in the theoretical description of strongly correlated materials. Most previous approaches considered the influence of intershell interactions at best in a static fashion, neglecting dynamic effects. In this work, we propose a slave-rotor method that goes beyond this approximation by incorporating the effect of intershell interactions in a dynamic manner. Our method is derived and implemented as a quantum impurity solver in the context of dynamical mean field theory and benchmarked on a two-orbital model system. The results from our slave-rotor technique are found to be in good agreement with our reference calculations that include intershell interactions explicitly. We identify and analyze qualitative features emerging from the dynamic treatment. Our results thus provide qualitatively new insights, revealing the ambivalent effect of intershell interactions in strongly correlated materials.