Current carrying edges in unconventional superconductors

While the bulk of a p or d wave superconductor does not carry any current, a current can run along the edges of a sample even in the absence of a magnetic field, unlike the case of a s wave superconductor. Such a current is often quantized and is independent of the magnitude of the gap. However, the existence of such a current violates Bloch's theorem. Here, we examine, by computation and analytic calculation, the question of the edge current in p and d wave superconductors in various geometries and the connection with the Bloch argument. The computation of the edge current also allows us to shed some light on the angular momentum paradox in the A phase of Helium 3.