Prediction of orbital selective Mott phases and block magnetic states in the quasi-one-dimensional iron chain Ce$_2$O$_2$FeSe$_2$ under hole and electron doping

TL;DR

This study models the electronic and magnetic phases of the quasi-one-dimensional iron chain Ce$_2$O$_2$FeSe$_2$ under doping, revealing orbital-selective Mott phases and various magnetic states, advancing understanding of iron-based chain materials.

Contribution

It introduces a three-orbital Hubbard model for Ce$_2$O$_2$FeSe$_2$, predicting orbital-selective Mott phases and magnetic states under doping, which were previously unexplored for this material.

Findings

Identification of orbital-selective Mott phases OSMP1 and OSMP2.

Prediction of diverse magnetic states including ferromagnetism and block phases.

Charge disproportionation phenomena at specific doping levels.

Abstract

The recent detailed study of quasi-one-dimensional iron-based ladders, with the $3d$ iron electronic density $n = 6$, has unveiled surprises, such as orbital-selective phases. However, similar studies for $n=6$ iron chains are still rare. Here, a three-orbital electronic Hubbard model was constructed to study the magnetic and electronic properties of the quasi-one-dimensional $n=6$ iron chain Ce$_2$O$_2$FeSe$_2$, with focus on the effect of doping. Specifically, introducing the Hubbard $U$ and Hund $J_{H}$ couplings and studying the model via the density matrix renormalization group, we report the ground-state phase diagram varying the electronic density away from $n=6$. For the realistic Hund coupling $J_{H}/U = 1/4$, several electronic phases were obtained, including a metal, orbital-selective Mott, and Mott insulating phases. Doping away from the parent phase, the competition of many tendencies leads to a variety of magnetic states, such as ferromagnetism, as well as several antiferromagnetic and magnetic "block" phases. In the hole-doping region, two different interesting orbital-selective Mott phases were found: OSMP1 (with one localized orbital and two itinerant orbitals) and OSMP2 (with two localized orbitals and one itinerant orbital). Moreover, charge disproportionation phenomena were found in special doping regions. We argue that our predictions can be tested by simple modifications in the original chemical formula of Ce$_2$O$_2$FeSe$_2$.