Orbital selective phase transition induced by different magnetic states: A dynamical cluster approximation study

TL;DR

This study investigates how different magnetic states in a two-orbital Hubbard model induce orbital selective phase transitions, revealing complex behaviors relevant to Fe-based superconductors.

Contribution

It demonstrates the occurrence of orbital selective phase transitions driven by magnetic states using a dynamical cluster approximation, independent of Hund's coupling strength.

Findings

Orbital selective phase transitions occur regardless of Hund's coupling.

The paramagnetic orbital transitions from Fermi liquid to Mott insulator.

The antiferromagnetic orbital transitions from Fermi liquid to antiferromagnetic insulator.

Abstract

Motivated by the unexplored complexity of phases present in the multiorbital Hubbard model, we analyze in this work the behavior of a degenerate two-orbital anisotropic Hubbard model at half filling where both orbitals have equal bandwidths and one orbital is constrained to be paramagnetic (PM), while the second one is allowed to have an antiferromagnetic (AF) solution. Such a model may be relevant for a large class of correlated materials with competing magnetic states in different orbitals like the recently discovered Fe-based superconductors. Using a dynamical cluster approximation we observe that novel orbital selective phase transitions appear regardless of the strength of the Ising Hund's rule coupling $J_z$. Moreover, the PM orbital undergoes a transition from a Fermi liquid (FL) to a Mott insulator through a non-FL phase while the AF orbital shows a transition from a FL to an AF insulator through an AF metallic phase. We discuss the implications of the results in the context of the Fe-based superconductors.