Hund?s coupling and crystal field effects in the coherence scale of three-orbital systems

JORGE I. FACIO; V. VILDOSOLA; PABLO S. CORNAGLIA

Julich

Workshop; Autumn School on Correlated Electrons: DMFT at 25, Infinite Dimensions; 2014

Forschungszentrum Juelich

While the role of Hund?s coupling (J) is well known in atoms, its consequences in solids have only been recently addressed in detail . Two key ingredients have been outlined: First, at half-filling, the critical Coulomb repulsion of the Mott transition, U C , is strongly reduced by J, while it is enhanced for any other filling. Second, for fillings larger than one and away from half-filling, J also causes a strong reduction of the quasiparticle weight. This gives place to a correlated phase with a low coherence scale which is yet far from Mott?s metal-insulator transition. These effects have been shown to be relevant in transition metal oxides as ruthenates as well as in iron pnictides and chalcogenides. In this work we study the effects of Hund?s coupling in a three orbital Kanamori Hamiltonian in the framework of dynamical mean field theory using the Rotationally Invariant Slave Bosons technique as impurity solver. Thistechnique allows an analysis of the low energy properties of the model. In particular we analyze the effects on the coherence scale of a crystal field that breaks the equivalence of the three orbitals and find that the Hund?s coupling and the crystal field stabilize in a broad range of filling an orbital selective Mott phase.