HE-3-B IN A THIN-FILM - A COMPARISON OF BOUNDARY-CONDITIONS

We calculate the gap function of stationary B-phase He-3 confined to a thin film and resting on a diffuse substrate with a freestanding upper surface. We employ two different formulations of the boundary conditions describing rough walls and compute the gap for various widths and surface roughnesses. Both formulations predict the abrupt vanishing of the perpendicular gap component at a width of about 2.5 coherence lengths irrespective of surface diffusivity. The parallel gap component persists down to a much smaller width which is quite roughness sensitive.