Electronic phase separation in iron pnictides

TL;DR

This paper proposes a mechanism for electronic phase separation in iron pnictides driven by competing spin-density-wave phases due to imperfect Fermi surface nesting, leading to inhomogeneous magnetic states.

Contribution

It introduces a model showing how competition between commensurate and incommensurate SDW phases causes phase separation in iron pnictides.

Findings

Uniform state becomes unstable under certain conditions.

Inhomogeneous states consist of coexisting SDW phases.

Qualitative agreement with experimental observations.

Abstract

A mechanism for electronic phase separation in iron pnictides is proposed. It is based on the competition between commensurate and incommensurate spin-density-wave phases in a system with an imperfect doping-dependent nesting of a multi-sheeted Fermi surface. We model the Fermi surface by two elliptical electron pockets and three circular hole pockets. The interaction between a charge carrier in a hole band and a carrier in an electron band leads to the formation of spin-density-wave order. The commensurate spin density wave in the parent compound transforms to the incommensurate phase when doping is introduced. We show that, for certain parameter values, the uniform state is unstable with respect to phase separation. The resulting inhomogeneous state consists of regions of commensurate and incommensurate spin-density-wave phases. Our results are in qualitative agreement with recent observations of incommensurate spin density waves and electronic inhomogeneity in iron pnictides.