Magnetization and spin-spin energy diffusion in the XY model: a diagrammatic approach |
| |
Authors: | Greenbaum Daniel |
| |
Institution: | Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. daniel.greenbaum@weizmann.ac.il |
| |
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. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|