Double-Exchange Model: Phase Diagram at Zero-Temperature

TL;DR

This paper presents a comprehensive zero-temperature phase diagram for the double exchange model with classical spins, revealing a stable spin-spiral state emerging from a continuous transition, especially at low carrier densities.

Contribution

It provides the first analytical zero-temperature phase diagram of the double exchange model across all parameters, including the identification of a stable spin-spiral phase.

Findings

Identifies a continuous phase transition from ferromagnetic to textured states.

Discovers a stable spin-spiral phase at low carrier density.

Shows the spin-spiral state is energetically favored over phase separation.

Abstract

The analytical zero-temperature phase diagram of the double exchange model for classical background spins as a function of the carrier density and Hund's coupling in the entire range of these parameters is presented. By constructing a continuum field theory we explore the possibility of a continuous phase transition from ferromagnetic state to a gently varying textured state. We find such a transition in and below two dimensions and show that the emerging stable state is a spin-spiral which survives the tendency towards phase separation into commonly considered phases, and is also energetically favored to the canted state, for low carrier density.