Year: 2012
Type: article
Abstract: Effect of rotationally invariant Hund's rule coupling on a magnetism of multiorbital Hubbard models is studied within a dynamical mean-field theory framework. Comparison of static magnetic susceptibilities and local densities of states of two- and three-orbital models of a complete rotationally invariant Coulomb interaction and a ``density-density'' Hartree type interaction shows the different role of spin-flip interactions for different band fillings. In the particle-hole symmetric case, the Mott-Hubbard physics dominates due to the strong effective Coulomb interaction, while for the multiple electronic configurations away from half-filling (two electrons in the three-band model) the formation of local magnetic moments due to Hund's exchange interaction becomes the most significant effect for itinerant magnetic systems. A shift of the temperature of magnetic ordering due to the rotationally invariant Hund's rule coupling is found to be the largest in a three-orbital model with a two-electron occupancy where the single particle spectrum is metallic and is not sensitive to different forms of the Coulomb vertex. A larger enhancement of the effective mass in a model with a rotationally invariant interaction is discussed. In the half-filled case we find a drastic change in the density of states close to the Mott transition which is related to the spin-flip Kondo fluctuations in a degenerate orbital case, while the corresponding shift of the magnetic transition temperature is relatively small. It is shown that a change in the ground-state degeneracy due to a different symmetry of the Coulomb interaction in the density-density model leads to a breakdown of the quasiparticle peak at the Fermi level in the proximity of a Mott transition on the metallic side. We discuss the relevance of rotationally invariant Hund's interaction in the transition metal magnetism.
Source: Physical Review B
Institutions: Max Planck Institute for Chemical Physics of Solids, Max Planck Institute for the Physics of Complex Systems, Centre National de la Recherche Scientifique, École Polytechnique, Centre de Physique Théorique, Ural Federal University, M.N. Mikheev Institute of Metal Physics, Universität Hamburg, Lomonosov Moscow State University
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1968969170