Superfluid Fraction in Thin Helium Films

Abstract
A shear-mode quartz-crystal microbalance measures only the nonsuperfluid component of the helium film adsorbed on it. From this effect detailed curves of the superfluid content in such films are obtained as functions of the total film mass adsorbed per unit area and of temperature. Besides the characteristic linear growth region of superfluid with thickness, these curves reveal the quantitative details of the onset region. Our results are presented together with some characteristic helium parameters deduced from them.