Intermittent Switching between Potential Flow and Turbulence in Superfluid Helium at mK Temperatures

摘要

Superfluid flow around an oscillating microsphere is investigated attemperatures down to 25 mK. Stable laminar flow below a critical velocity andturbulence at large drives are found to be separated below 0.5 K by anintermediate range of driving forces where the flow is unstable, intermittentlyswitching between laminar and turbulent phases. We have recorded time series ofthis switching phenomenon and have made a statistical analysis of the switchingprobability. The mean lifetime of the turbulent phases grows with increasingdrive and becomes infinite at a critical value. Stability of the laminar phasesabove the critical velocity is limited by natural background radioactivity orcosmic rays.