Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach
Abstract
It is shown that the diagrammatic cluster expansion technique for equilibrium averages of spin operators may be straightforwardly extended to the calculation of time-dependent correlation functions of spin operators. We use this technique to calculate exactly the first two non-vanishing moments of the spin-spin and energy-energy correlation functions of the XY model with arbitrary couplings, in the long-wavelength, infinite temperature limit appropriate for spin diffusion. These moments are then used to estimate the magnetization and spin-spin energy diffusion coefficients of the model using a phenomenological theory of Redfield. Qualitative agreement is obtained with recent experiments measuring diffusion of dipolar energy in calcium fluoride.
Cite
@article{arxiv.cond-mat/0511399,
title = {Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach},
author = {Daniel Greenbaum},
journal= {arXiv preprint arXiv:cond-mat/0511399},
year = {2007}
}
Comments
28 pages, 15 embedded .eps figures, Elsevier preprint format