Spinon deconfinement above a finite energy gap in two-dimensional quantum Heisenberg antiferromagnets

The familiar spin-1/2 quantum Heisenberg antiferromanget in a two-dimensional (2D) square lattice is shown, within the nonlinear sigma model approximations, to be another state of matter that has excitations with fractional quantum numbers above a finite energy gap. The 1-skyrmion with an energy approximate to2piJ is shown to be made of two deconfined spinons or O(3) vortices. The many skyrmion operator and the wave functions that we have found are strikingly similar to quantum Hall quasiparticle operators and wave functions. We also predict the presence of finite energy spin-S spinon for a general spin S Heisenberg antiferromagnets in 2D. Some consequences are briefly discussed.