Experiments on ${}^4\mathrm{He}$ films reveal an attractive Casimir-like force at the bulk $\lambda$ point and in the superfluid regime. Previous work has explained the magnitude of this force at the $\lambda$ transition and deep in the superfluid region but not the substantial attractive force immediately below the $\lambda$ point. Utilizing a simple mean-field calculation renormalized by critical fluctuations we obtain an effective Casimir force that is qualitatively consistent with the scaling function $\vartheta$ obtained by collapse of experimental data.

• Received 24 January 2007

DOI:https://doi.org/10.1103/PhysRevE.76.030601