Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach

Daniel Greenbaum

doi:10.1016/j.jmr.2005.10.011

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Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach

Daniel Greenbaum

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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.

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Daniel Greenbaum. 2005-11-16. Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach. https://doi.org/10.1016/j.jmr.2005.10.011

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