Quantum depinning transition of quantum Hall stripes.

We examine the effect of disorder on the electromagnetic response of quantum Hall stripes using an effective elastic theory to describe their low-energy dynamics, and replicas and the Gaussian variational method to handle disorder effects. Within our model we demonstrate the existence of a depinning transition at a critical partial Landau level filling factor Deltanu(c). For Deltanu<Deltanu(c), the pinned state is realized in a replica symmetry breaking (RSB) solution, and the frequency-dependent conductivities both perpendicular and parallel to the stripes show resonant peaks. These peaks shift to zero frequency as Deltanu-->Deltanu(c). For Deltanu> or =Deltanu(c), we find a partial RSB solution in which there is free sliding only along the stripe direction. The transition is analogous to the Kosterlitz-Thouless phase transition.