Spin quantum Hall effect in unconventional superconductors

We study the properties of the ``spin quantum Hall fluid''---a spin phase with quantized spin Hall conductance that is potentially realizable in superconducting systems with unconventional pairing symmetry. A simple realization is provided by a d_x²-y²+idxy superconductor which we argue has a dimensionless spin Hall conductance equal to 2. A theory of the edge states of the d_x²-y²+idxy superconductor is developed. The properties of the transition to a phase with vanishing spin Hall conductance induced by disorder are considered. We construct a description of this transition in terms of a supersymmetric spin chain, and use it to numerically determine universal properties of the transition. We discuss various possible experimental probes of this quantum Hall physics.