Periodic Anderson model with degenerate orbitals: linearized dynamical mean field theory approach

TL;DR

This paper extends the periodic Anderson model to multiple orbitals, using a linearized dynamical mean-field theory to analyze electron correlations, orbital fluctuations, and phase transitions between Kondo and Mott insulators.

Contribution

It introduces a multi-orbital extension of the model and applies a linearized DMFT approach to study the effects of orbital fluctuations and Hund coupling.

Findings

Orbital fluctuations can enlarge the Kondo insulating gap under certain interaction conditions.

Hund coupling suppresses the enhancement of orbital fluctuations.

The transition from Kondo insulator to Mott insulator is clarified as electron correlations increase.

Abstract

We investigate a multi-orbital extension of the periodic Anderson model with particular emphasis on electron correlations including orbital fluctuations. By means of a linearized version of the dynamical mean-field theory, we compute the renormalization factor, the density of states, the spectral gap and the local correlation functions for a given set of the intra- and inter-orbital Coulomb interactions as well as the Hund coupling. It is found that when a certain condition is met for the intra- and inter-orbital interactions for $f$ electrons, orbital fluctuations are enhanced, thereby enlarging the Kondo insulating gap. This effect is suppressed in the presence of the Hund coupling. We also clarify how the Kondo insulator is continuously changed to the Mott insulator when electron correlations among conduction electrons are increased.