Dynamical generation of a gauge symmetry in the Double-Exchange model

TL;DR

This paper demonstrates that the double-exchange model can dynamically generate a gauge-invariant phase, with a transition line belonging to the universality class of the Antiferromagnetic RP(2) model, challenging traditional universality expectations.

Contribution

It introduces a bosonic formulation of the double-exchange model that reveals a dynamically generated gauge symmetry and characterizes its phase transition properties.

Findings

Identification of a gauge-invariant phase in the model

Transition line belongs to the Universality Class of the Antiferromagnetic RP(2) model

Contradicts naive expectations about universality classes

Abstract

It is shown that a bosonic formulation of the double-exchange model, one of the classical models for magnetism, generates dynamically a gauge-invariant phase in a finite region of the phase diagram. We use analytical methods, Monte Carlo simulations and Finite-Size Scaling analysis. We study the transition line between that region and the paramagnetic phase. The numerical results show that this transition line belongs to the Universality Class of the Antiferromagnetic RP(2) model. The fact that one can define a Universality Class for the Antiferromagnetic RP(2) model, different from the one of the O(N) models, is puzzling and somehow contradicts naive expectations about Universality.