Flow equation approach to heavy fermion systems

TL;DR

This paper applies Wegner's flow equation method to the infinite-U periodic Anderson model, revealing a new approach to understanding heavy fermion behavior through an effective Hamiltonian with decoupled degrees of freedom and gapped quasiparticle bands.

Contribution

It introduces a novel application of the flow equation method to heavy fermion systems, deriving an effective Hamiltonian and analyzing electronic structure and energy scales.

Findings

Identification of two gapped quasiparticle bands.

Exponential dependence of lattice Kondo temperature on hybridization.

Significant decrease of Kondo temperature compared to single impurity model.

Abstract

We use Wegner's flow equation method to investigate the infinite-$U$ periodic Anderson model. We show that this method poses a new approach to the description of heavy fermion behaviour. Within this scheme we derive an effective Hamiltonian where the $c$ and $f$ degrees of freedom are decoupled. By evaluating one-particle energies as well as correlation functions we find an electronic structure which comprises two gapped quasiparticle bands. We also address the lattice Kondo temperature, which shows a typical exponential dependence on the hybridisation energy. This energy scale exhibits a significant decrease compared to that of the single impurity Anderson model.