Skyrmions and Quantum Hall Ferromagnets inImproved Composite-Boson Theory

Abstract

An improved composite-boson theory of quantum Hall ferromagnets is proposed.It is tightly related with the microscopic wave-function theory. Thecharacteristic feature is that the field operator describes solely thephysical degrees of freedom representing the deviation from the groundstate.It presents a powerful tool to analyze excited states within the lowest Landau level.Excitations include a Goldstone mode and nonlocal topological solitons.Solitons are vortices and Skyrmions carrying the U(1) and SU(2) topologicalcharges, respectively. Their classical configurations are derived fromtheirmicroscopic wave functions. The activation energy of one Skyrmion isestimated, which explains experimental data remarkably well.