title: Critical Casimir force in 4He films: confirmation of finite-size scaling.
abstract: We present new capacitance measurements of critical Casimir force-induced thinning of 4He films near the superfluid transition, focused on the region below Tlambda where the effect is the greatest. 4He films of 238, 285, and 340 A thickness are adsorbed on atomically smooth, N-doped silicon substrates. The Casimir force scaling function theta, deduced from the thinning of these three films, collapses onto a single universal curve, attaining a minimum theta=-1.30+/-0.03 at x=td1/nu=-9.7+/-0.8 A1/nu. The collapse confirms the finite-size scaling origin of the dip in the film thickness. Separately, we also confirm the presence down to 2.13 K of the Goldstone or surface fluctuation force, which makes the superfluid film approximately 2 A thinner than the normal film.
authors.affiliation: Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: A
authors.initials: A
authors.lastname: Ganshin
authors.forename: S
authors.initials: S
authors.lastname: Scheidemantel
authors.forename: R
authors.initials: R
authors.lastname: Garcia
authors.forename: M H W
authors.initials: MH
authors.lastname: Chan