We present new capacitance measurements of critical Casimir force-induced thinning of 4He films near the superfluid transition, focused on the region below Tλ where the effect is the greatest. 4He films of 238, 285, and 340 Å thickness are adsorbed on atomically smooth, N-doped silicon substrates. The Casimir force scaling function ν, deduced from the thinning of these three films, collapses onto a single universal curve, attaining a minimum ν = -1:30 ± 0:03 at x = td1/ν= - 9:7 ± 0:8 Å 1/ν. 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 ∼2 Å thinner than the normal film.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)