Competition between the superfluidity and the slippage of 4He films adsorbed on porous gold

We have carried out QCM measurements for 4He films adsorbed on porous gold in the crossover region between the superfluidity and slippage. In relative low areal densities, the resonance frequency increases gradually below TS due to the slippage of solid film, while the superfluid onset is observed in high areal densities. In the crossover region, we observed a peuliar behavior: The inrease in the resonance frequency below TS is suddenly suppressed at a certain temperatue TD. From these observations, it is oncluded that the superfluidity and the slippage of 4He competes with eah other.