Quasiclassical Methods in the Linear Heisenberg Model.

Jill C. Bonner

Yao-Chung Chang, George C. Summerfield

Previous results of quasiclassical spin dynamics are extended by presenting a new approximation for quantum corrections to the classical equation of motion for the Heisenberg model. The accuracy of the equation with these corrections is determined by comparing computer calculations based on this formalism with exact quantum and classical results for spin pair correlation functions for a six-spin linear chain at infinite temperatures.

Minoru Takahashi

R. E. Prange

Yao-Chung Chang, George C. Summerfield, D. M. Kaplan

The Wigner method is employed to develop explicit relationships among quantum-mechanical and classical equations of motion and quantum-mechanical and classical pair-correlation functions of spin operators. In this method, quantum corrections to the classical theory can be accurately estimated. The formalism is applied to a spin-\textonehalf{} Heisenberg model at high temperatures. The most attractive feature of this method is that many of the results are intuitively satisfying. Finally, we make a connection between our results and the classical calculations made by several other authors.

A. G. Antipov, Igor V. Komarov

The quantum method of variable separation is applied to the spectral problem of the isotropic Heisenberg model. The Baxter difference equation is resolved by means of a special quasiclassical asymptotic expansion. States are identified by multiplicities of limiting values of the Bethe parameters. The string limit of the four-particle sector is investigated. String solutions are singled out and classified. It is shown that only a minor fraction of solutions demonstrate string behavior.