Spatial fluctuations of spin and orbital in two-orbital Hubbard model

TL;DR

This study explores the quasiparticle behavior in a two-orbital Hubbard model, revealing how Hund's coupling influences orbital correlations, pseudogap formation, and temperature-dependent quasiparticle dynamics.

Contribution

It provides new insights into the effects of Hund's coupling on orbital fluctuations and quasiparticle properties in a two-orbital Hubbard model at quarter filling.

Findings

Fermi-liquid state is stable up to large interactions without Hund's coupling.

Hund's coupling enhances antiferro-orbital correlations and pseudogap behavior.

Quasiparticle dynamics show nonmonotonic temperature dependence due to competing effects.

Abstract

We investigate the quasiparticle dynamics in the two-orbital Hubbard model on the square lattice at quarter filling by means of the cellular dynamical mean field theory. We show that the Fermi-liquid state is stabilized up to the large Hubbard interactions in the symmetric case without the Hund's coupling, and find the heavy quasiparticles around the metal-insulator boundary. It is elucidated that the Hund's coupling enhances the antiferro-orbital correlations, which give rise to the pseudo gap behavior in the single-particle excitations. We also find the nonmonotonic temperature dependence in the quasiparticle dynamics for intermediate strength of the Hund's coupling, and clarify that it is caused by the competition between the Fermi-liquid formation and the antiferro-orbital fluctuations.