Collective excitations, NMR, and phase transitions in Skyrme crystals

At Landau level filling factors near nu = 1, quantum Hall ferromagnets form a Skyrme crystal state with quasi-long-range translational and noncollinear magnetic order. We develop an effective low energy theory which explains the presence of magnetic excitations in these systems at energies below the Larmor gap (Delta) and that predicts a dramatic enhancement of the nuclear spin relaxation rate by a factor of 10(3). The effective theory predicts a rich set of quantum and classical phase transitions. Based in part on accurate time-dependent Hatree-Fock calculations of the ordered state collective excitation spectrum, we discuss aspects of the T-nu-Delta Skyrme crystal phase diagram.