We discuss a systematic, microscopic calculation of the spin-stiffness constants for the spin-(1/2 square-lattice Heisenberg antiferromagnet. An infinitesimal twist is imposed upon the system by gradually rotating the direction of antiferromagnetic ordering. The difference in the ground-state energy of this system with respect to the uniformly ordered ground state can be related to the spin-stiffness constants. Series expansions and extrapolation for the energy of the twisted system lead to the estimate &s/J)=0.720.0. The ratio of the series for s and perpendicular susceptibility leads to an estimate for the spin-wave &(=cs/ 2 J)=1.180.02. The experiments on La2CuO4 are quantitatively consistent with a nearest-neighbor Heisenberg model when one takes into account these quantum renormalizations.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics