Lifting mean-field degeneracies in anisotropic classical spin systems
Abstract
In this work, we propose a method for calculating the free energy of anisotropic classical spin systems. We use a Hubbard-Stratonovich transformation to express the partition function of a generic bilinear super-exchange Hamiltonian in terms of a functional integral over classical time-independent fields. As an example, we consider an anisotropic spin-exchange Hamiltonian on the cubic lattice as is found for compounds with strongly correlated electrons in multiorbital bands and subject to strong spin-orbit interaction. We calculate the contribution of Gaussian spin fluctuations to the free energy. While the mean-field solution of ordered states for such systems usually has full rotational symmetry, we show here that the fluctuations lead to a pinning of the spontaneous magnetization along some preferred direction of the lattice.
Keywords
Cite
@article{arxiv.1503.04507,
title = {Lifting mean-field degeneracies in anisotropic classical spin systems},
author = {Yuriy Sizyuk and Natalia B. Perkins and Peter Wölfle},
journal= {arXiv preprint arXiv:1503.04507},
year = {2016}
}
Comments
Results for the intermediate phase with minima and maxima "dancing" around each other, which were presented in Fig.2 and Fig.3 in the previous version of the paper, were wrong due to numerical error. We removed these figures from the current version and modified the corresponding discussion. We send the erratum note for publication in PRB