NONLINEAR SIGMA-MODEL FOR PARTIALLY POLARIZED QUANTUM HALL STATES

We consider a two-component quantum Hall system within a Landau-Ginzbu rg theory with two Chern-Simons gauge fields. From this theory we deri ve a sigma model covariantly coupled to one Chern-Simons field and fin d mean-field solutions that could describe partially polarized quantum Hall states. The quasiparticles in the original model, which have qua ntized charge and spin, are described in the covariant sigma model by topological excitations, with the correct quantum numbers. They have f inite energy due to the presence of the Chem-Simons field, and closely resemble the skyrmions in the usual nonlinear sigma model. For the fu lly polarized states the spin is no longer quantized, but determined b y Coulomb and Zeeman interactions.