Anisotropic two-orbital Hubbard model: single-site versus cluster dynamical mean-field theory

TL;DR

This paper compares single-site and cluster dynamical mean-field theories applied to an anisotropic two-orbital Hubbard model, revealing complex phases and discussing implications for iron-pnictide superconductors.

Contribution

It provides a detailed analysis of the differences between single-site DMFT and DCA in studying a complex multi-orbital model, highlighting their respective advantages and limitations.

Findings

Identification of orbital selective phase transitions

Observation of non-Fermi liquid behavior

Detection of antiferromagnetic metallic states

Abstract

The anisotropic two-orbital Hubbard model with different bandwidths and degrees of frustration in each orbital is investigated in the framework of both single-site dynamical mean-field theory (DMFT) as well as its cluster extension (DCA) for clusters up to four sites combined with a continuous-time quantum Monte Carlo algorithm. This model shows a rich phase diagram which includes the appearance of orbital selective phase transitions, non-Fermi liquid behavior as well as antiferromagnetic metallic states. We discuss the advantages and drawbacks of employing the single-site DMFT with respect to DCA and the consequences for the physical picture obtained out of these calculations. Finally, we argue that such a minimal model may be of relevance to understand the nature of the antiferromagnetic metallic state in the iron-pnictide superconductors as well as the origin of the small staggered magnetization observed in these systems.