Possible origin of the reduced magnetic moment in iron pnictides: A dynamical mean field theory study

TL;DR

This study uses dynamical mean field theory to explore phase transitions in a two-band frustrated Hubbard model, revealing intermediate phases that may explain the small-magnetization antiferromagnetic state in iron-pnictide superconductors.

Contribution

It demonstrates the emergence of orbital-selective intermediate phases in a two-band Hubbard model, providing insights into the magnetic properties of iron-pnictides.

Findings

First-order transition from paramagnetic metal to antiferromagnetic insulator when both bands are frustrated.

Intermediate antiferromagnetic metallic phases appear when only one band is frustrated.

Potential explanation for the small-magnetization AF state and pseudogap features in iron-pnictides.

Abstract

We investigate the phase diagram of a two-band frustrated Hubbard model in the framework of dynamical mean field theory. While a first-order phase transition occurs from a paramagnetic (PM) metal to an antiferromagnetic (AF) insulator when both bands are equally frustrated, an intermediate AF metallic phase appears in each band at different $U_c$ values if only one of the two bands is frustrated, resulting in continuous orbital-selective phase transitions from PM metal to AF metal and AF metal to AF insulator. We argue that such intermediate phases are possibly related to the puzzling AF metallic state with small magnetization observed in undoped iron-pnictide superconductors as well as to the pseudogap features observed in optical experiments.