Interaction Effect in the Kondo Energy of the Periodic Anderson-Hubbard Model

TL;DR

This paper investigates how adding Hubbard interaction to conduction electrons in the Anderson model affects the Kondo energy, revealing suppression effects and a transition from Kondo insulator to Mott insulator at half-filling.

Contribution

It introduces a new formula for Kondo energy incorporating Hubbard U effects and explores the resulting phase transition in the extended model.

Findings

Hubbard U suppresses the Kondo scale.

A Brinkman-Rice transition occurs at half-filling.

Transition from Kondo insulator to Mott insulator is identified.

Abstract

We extend the periodic Anderson model by switching on a Hubbard $U_d$ for the conduction electrons. The nearly integral valent (Kondo) limit of the Anderson--Hubbard model is studied with the Gutzwiller variational method. The new formula for the Kondo energy contains the $U_d$-dependent chemical potential of the Hubbard subsystem in the exponent, and the correlation-induced band narrowing in the prefactor. Both effects tend to suppress the Kondo scale, which can be understood to result from the blocking of hybridization (this behaviour is the opposite of that found for Kondo--Hubbard models). At half-filling, we find a Brinkman--Rice-type transition which leads from a small-gap Kondo insulator to a Mott insulator.