Hund's coupling and the metal-insulator transition in the two-band Hubbard model

TL;DR

This paper investigates how Hund's coupling influences the Mott-Hubbard metal-insulator transition in a two-band Hubbard model using an advanced non-perturbative numerical method within dynamical mean-field theory.

Contribution

It introduces an extension of Wilson's numerical renormalization group to accurately include Hund's rule coupling effects in the two-band Hubbard model.

Findings

Hund's coupling significantly affects the Mott transition.

The method captures full exchange interactions.

Thermodynamic and dynamic properties are detailed.

Abstract

The Mott-Hubbard metal-insulator transition is investigated in a two-band Hubbard model within dynamical mean-field theory. To this end, we use a suitable extension of Wilson's numerical renormalization group for the solution of the effective two-band single-impurity Anderson model. This method is non-perturbative and, in particular, allows to take into account the full exchange part of the Hund's rule coupling between the two orbitals. We discuss in detail the influence of the various Coulomb interactions on thermodynamic and dynamic properties, for both the impurity and the lattice model. The exchange part of the Hund's rule coupling turns out to play an important role for the physics of the two-band Hubbard model and for the nature of the Mott-transition.