S(Q,OMEGA) FOR THE S = 1/2 AND S = 1 ONE-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET - A QUANTUM MONTE-CARLO STUDY

The dynamic-spin-correlation function S(q,) is computed for the one-dimensional antiferromagnetic Heisenberg model for S=1/2 and S=1. Imaginary-time correlation functions are evaluated with the quantum Monte Carlo method and the maximum-entropy method is used to continue these results to real frequencies. This technique produces a value for the S=1 Haldane gap that agrees with previous work and also gives a good description of inelastic neutron scatter- ing data for the one-dimensional S=1/2 antiferromagnet CuCl2 2N(C5D5). © 1990 The American Physical Society.