Some phenomenological theoretical aspects of intrinsic superfluid critical velocities

Abstract

We use a phenomenological theory of superfluid critical velocities in small orifices to explain three phenomena: (1) The low-temperature intrinsic critical velocity ${\mathit{v}}_{\mathit{c}}$ in dc experiments should depend logarithmically on the driving pressure head; the logarithmic increment in ${\mathit{v}}_{\mathit{c}}$ is the width of the velocity distribution function for phase slips. (2) The critical velocity measured in dc experiments is related to that seen in ac experiments through the quantum number of the phase slips involved. (3) It is possible that quantum tunneling processes may be significant at temperatures as high as 0.3 K.