Zigzag and Checkerboard Magnetic Patterns in Orbitally Directional Double-Exchange Systems

TL;DR

This paper investigates how orbital directionality in a $t_{2g}$ double-exchange system leads to distinct zigzag and checkerboard magnetic patterns, revealing a doping-induced metal-insulator transition driven by orbital molecules.

Contribution

It introduces a new understanding of how orbital directionality influences magnetic orderings and phase transitions in double-exchange systems, emphasizing the role of structural distortions and Coulomb interactions.

Findings

Orbital molecules favor zigzag states over metallic stripes.

Doping induces a transition from metal to insulator.

Structural distortions break orbital directionality affecting magnetic phases.

Abstract

We analyze a $t_{2g}$ double-exchange system where the orbital directionality of the itinerant degrees of freedom is a key dynamical feature that self-adjusts in response to doping and leads to a phase diagram dominated by two classes of ground-states with zigzag and checkerboard patterns. The prevalence of distinct orderings is tied to the formation of orbital molecules that in one-dimensional paths make insulating zigzag states kinetically more favorable than metallic stripes, thus allowing for a novel doping-induced metal-to-insulator transition. We find that the basic mechanism that controls the magnetic competition is the breaking of orbital directionality through structural distortions and highlight the consequences of the interorbital Coulomb interaction.