Orbital-selective Mott-Hubbard transition in the two-band Hubbard model

TL;DR

This paper uses advanced quantum Monte Carlo simulations within dynamical mean field theory to confirm the existence of an orbital-selective Mott-Hubbard transition in a two-band Hubbard model, clarifying the nature of this transition.

Contribution

It demonstrates the existence of an orbital-selective Mott-Hubbard transition with SU(2) Hund's exchange, resolving previous controversies about its nature.

Findings

Wide band remains metallic after narrow band becomes insulating.

Transition is generally first-order, with coexistence of metallic and insulating solutions.

Contrasts with pseudogap behavior seen with Ising Hund's exchange.

Abstract

Recent advances in the field of quantum Monte Carlo simulations for impurity problems allow --within dynamical mean field theory-- for a more thorough investigation of the two-band Hubbard model with narrow/wide band and SU(2)-symmetric Hund's exchange. The nature of this transition has been controversial, and we establish that an orbital-selective Mott-Hubbard transition exists. Thereby, the wide band still shows metallic behavior after the narrow band became insulating -not a pseudogap as for an Ising Hund's exchange. The coexistence of two solutions with metallic wide band and insulating or metallic narrow band indicates, in general, first-order transitions.