Itinerant electrons in the Coulomb phase

TL;DR

This paper investigates how itinerant electrons interact with magnetic frustration in Coulomb phases, revealing how electron doping influences loop structures and conductivity, with implications for understanding spin liquids and magnetic materials.

Contribution

It provides an analytical and simulation-based study of electron coupling in Coulomb phases, highlighting the emergence of magnetic loops as conducting channels and their evolution with doping.

Findings

Magnetic loops act as conduction pathways influenced by electron doping.

Doping causes segmentation and rearrangement of loops, reducing degeneracy.

Lattice dependence leads to distinct loop crystal formations and melting behaviors.

Abstract

We study the interplay between magnetic frustration and itinerant electrons. For example, how does the coupling to mobile charges modify the properties of a spin liquid, and does the underlying frustration favor insulating or conducting states? Supported by Monte Carlo simulations, our goal is in particular to provide an analytical picture of the mechanisms involved. The models under considerations exhibit Coulomb phases in two and three dimensions, where the itinerant electrons are coupled to the localized spins via double exchange interactions. Because of the Hund coupling, magnetic loops naturally emerge from the Coulomb phase and serve as conducting channels for the mobile electrons, leading to doping-dependent rearrangements of the loop ensemble in order to minimize the electronic kinetic energy. At low electron density \rho, the double exchange coupling mainly tends to segment the very long loops winding around the system into smaller ones while it gradually lifts the extensive degeneracy of the Coulomb phase with increasing \rho. For higher doping, the results are strongly lattice dependent, displaying loop crystals with a given loop length for some specific values of \rho, which can melt into another loop crystal by varying \rho. Finally, we contrast this to the qualitatively different behavior of analogous models on kagome or triangular lattices.