Competition Between the Superfluid Overlayer and the Mobile Solid Layer of ~3He-~4He Mixture Films on Porous Gold

摘要

In the previous quartz crystal microbalance measurements for ~4He films adsorbed on porous gold, we have observed a competition between superfluidity and slippage: In low areal densities, the resonance frequency increases gradually below T_S due to the slippage of solid layer, while at high areal densities the slippage disappears and the superfluid onset of liquid overlayer is observed at T_C. In the crossover region, the slippage below T_S is suddenly suppressed at T_D, which is much lower than T_C. In the present work, we introduced a small amount of ~3He onto ~4He films, and studied the competition as a function of ~3He areal density ρ_3. As ρ_3 is increased, T_C is monotonically lowered. In contrast, T_D increases up to a certain value of ρ_3, and then turns over to decrease in parallel to T_C.