Slippage of Nonsuperfluid 3He-4He Mixture Film on Gold

Abstract

We report the result of a QCM experiment at 100 MHz for a coverage of 3He-4He mixture film (n3 = 0.75 and n4 = 2.90 bulk-density layers) on a planar gold substrate. This study is done by taking the temperature scan of both warming and cooling at various constant oscillation velocities v from 19 to 59 μm/s. At minimum v = 19 μm/s, a frequency shift of about 5 Hz due to the superfluid transition is observed below the onset temperature To = 0.16 K Surprisingly, at v = 35 μm/s, the observation is dramatically changed and an extra large frequency shift with a hysteresis loop between warming and cooling is found. Upon increasing v further, the extra shift evolves into much larger shifts. These observations suggest that a part of 3He on underlying 4He layer slips by a pinning-depinning mechanism above v = 35 μm/s. At maximum v = 59 μm/s, the decoupling ratio of slippage reaches 90% of the whole 3He population.