Exact calculation of the ground-state dynamical spin correlation function of a S=1/2 antiferromagnetic Heisenberg chain with free spinons

摘要

We calculate the exact dynamical magnetic structure factor S(Q,E) in theground state of a one-dimensional S=1/2 antiferromagnet with gapless free S=1/2spinon excitations, the Haldane-Shastry model with inverse-square exchange,which is in the same low-energy universality class as Bethe's nearest-neighborexchange model. Only two-spinon excited states contribute, and S(Q,E) is foundto be a very simple integral over these states.