Stability of Composite Fermions to Disorder*

A significant problem in Quantum Hall physics concerns the effects of disorder on the global phase diagram. The stability of incompressible states to a small amount of disorder is well-known. However, the fate of compressible states that occur, for example, near even denominator fillings in the presence of disorder remains poorly understood. We use the theory of composite fermions to analyze this problem. Because composite fermions carry both charge and flux, quenched disorder must involve both random potentials and random magnetic fields. Treating gauge fluctuations within a mean-field approximation, we present numerical and analytical studies of nearly free particles in the presence of both random potential and flux.