Localization of spin waves in the quantum Hall ferromagnet

The topological nature of the quantized Hall plateau has a number of remarkable consequences. For the quantum Hall ferromagnet (QHF), it leads to the identification of the topological charge density of a spin distortion with the associated electrical charge density. Spin waves may couple to a scalar disorder potential via their topological density. This interaction is very similar to minimal coupling of quantum particles to a random fur. It leads to the localization of spin waves in the QHF. We derive a low-energy description of the system in terms of a nonlinear sigma-model of unitary supermatrices. A possible experimental signature of these effects in photoemission is suggested.