Competing orders in FeAs layers

TL;DR

This paper investigates the complex phase diagram of FeAs layers, identifying multiple competing magnetic and charge-ordered phases near half-filling, including a novel non-collinear magnetic phase, using theoretical models.

Contribution

It introduces a new magnetic phase with orthogonal moments and explores the rich competition among phases in FeAs layers near half-filling.

Findings

First-order transition from paramagnet to magnetic phase near half-filling

Discovery of a new non-trivial magnetic phase with orthogonal moments

Identification of a phase with magnetic and charge order stabilized by impurities

Abstract

Using the unrestricted Hartree-Fock approximation and Landau theory we identify possible phases competing with superconductivity in FeAs layers. We find that close to half-filling the transition from the paramagnet to the magnetically ordered phase is first-order making anharmonicities relevant and leading to a rich phase diagram. Between the already known one dimensionally modulated magnetic stripe phase and the paramagnet we find a new phase which has the same structure factor as the former but in which magnetic moments at nearest-neighbor sites are at right angles making electrons to acquire a non trivial phase when circulating a plaquette at strong coupling. Another competing phase has magnetic and charge order and may be stabilized by charged impurities.