Critical Casimir effect in dilute 3He–4He mixture films

Abstract Recently, we have found that 4 He films thin near the lambda point. Based on our measurements, the thinning appears to be caused by the confinement of superfluid order parameter fluctuations in the films. The phenomenon of the thinning is believed to be analogous to the Casimir effect in electromagnetism where the confinement of electromagnetic fluctuations causes the vacuum layer that separates two metal plates to thin. In this paper, we report the result of an experiment extending our previous study to 3 He– 4 He mixture films. Thinning is found near the new lambda points and the characteristics of the thinning are similar to that found in pure 4 He films.