- Published 1997

We calculate the nuclear relaxation rate 1/TO 1 of oxygen in the undoped quasi two-dimensional quantum Heisenberg antiferromagnet Sr2CuO2Cl2 above the Neel temperature. The calculation is performed at two-loop order with the help of the Dyson-Maleev formulation of the spin-wave expansion, taking all scattering processes involving two and three magnons into account. At low temperatures T we find 1/TO 1 = c1T 3 + c2T 4 + O(T 5), and give explicit expressions for the coefficients c1 (two-magnon scattering) and c2 (three magnon scattering). We compare our result with a recent experiment by Thurber et al. and argue that this experiment directly probes the asymptotic freedom of short-wavelength magnons in a two-dimensional antiferromagnet. PACS numbers: 76.60.-k, 75.10Jm, 75.30Ds, 74.25.Ha Typeset using REVTEX 1

@inproceedings{Kopietz1997TheNR,
title={The NMR relaxation rate of O in undoped Sr2CuO2Cl2: Probing the asymptotic freedom of two-dimensional magnons},
author={Peter Kopietz and Sudip Chakravarty},
year={1997}
}