Exhaustion physics in the periodic Anderson model from iterated perturbation theory

We discuss the "exhaustion" problem in the context of the periodic Anderson model using iterated perturbation theory (IPT) within the dynamical mean-field theory. We find that, despite its limitations, IPT captures the exhaustion physics, which manifests itself as a dramatic, strongly energy-dependent, suppression of the effective hybridization of the self-consistent Anderson impurity problem. As a consequence, low-energy scales in the lattice case are strongly suppressed compared to the "Kondo scale" in the single impurity picture. The IPT results are in qualitative agreement with recent Quantum Monte Carlo results for the same problem

Nonlocal dynamical correlations of strongly interacting electron systems

We introduce an extension of the dynamical mean-field approximation (DMFA) that retains the causal properties and generality of the DMFA, but allows for systematic inclusion of nonlocal corrections. Our technique maps the problem to a self-consistently embedded cluster. The DMFA (exact result) is recovered as the cluster size goes to 1 (infinity). As a demonstration, we study the Falicov-Kimball model using a variety of cluster sizes. We show that the sum rules are preserved, the spectra are positive definite, and the nonlocal correlations suppress the charge-density wave transition temperature