Implications of the Low-Temperature Instability of Dynamical Mean Theory for Double Exchange Systems

TL;DR

This paper reveals a previously unnoticed low-temperature instability in dynamical mean field theory applied to double exchange systems, which can help identify phase separation regimes efficiently.

Contribution

It uncovers a new local fluctuation-driven instability in the dynamical mean field approximation for the double exchange model, linking it to phase separation detection.

Findings

Identifies a low-temperature instability in the DMFT approximation.

Shows the instability is linked to phase separation or competing phases.

Proposes the instability as a computational tool for phase separation regimes.

Abstract

The single-site dynamical mean field theory approximation to the double exchange model is found to exhibit a previously unnoticed instability, in which a well-defined ground state which is stable against small perturbations is found to be unstable to large-amplitude but purely local fluctuations. The instability is shown to arise either from phase separation or, in a narrow parameter regime, from the presence of a competing phase. The instability is therefore suggested as a computationally inexpensive means of locating regimes of parameter space in which phase separation occurs.