A Chemical Potential “Battery” for Superfluid 4He Weak Links

Research and development of superfluid weak links has been hindered by the absence of a source of dc chemical potential, similar to a simple battery or voltage source for analogous superconducting devices. We describe here a method for generating a dc chemical potential difference, Δμ across a weak link array in superfluid 4He. The presence of a Δμ forces quantum oscillations at a Josephson frequency, selectable by the adjustment of input power to a heater. We discuss a case in which the frequency locks onto a resonance feature where it exhibits remarkable stability, and amplitude magnification by a factor of 40.