Critical Casimir Forces :-

 

One of the most beautiful aspects of physics is how phenomena in widely different systems are described by the same mathematical formulation. In electromagnetism, the Casimir force is due to the confinement of zero-point electromagnetic fluctuations between two conducting plates a finite distance apart. In a completely analogous way, the confinement of critical fluctuation in an adsorbed film leads a thickness dependence correction to the free energy of the film and, therefore a critical Casimir force between the interfaces of the film.

         The existence of the critical Casimir force was confirmed by Rafael Garcia by measuring the thickness of ⁴He film adsorbed on copper as the system is brought through the superfluid , or lambda ,transition. A thinning of the adsorbed film driven by the attractive force between the liquid-vapor and the liquid-copper interface is found (1). Subsequently a repulsive critical Casimir force near the ³He-⁴He tricritical point is found (2). Experiments are currently in progress to refine these experiments by studying films adsorbed on atomically flat silicon surfaces.

 

[1] R. Garcia and M.H.W. Chan, Phys. Rev. Letts. 83, 1187 (1999)

[2] R. Garcia and M.H.W. Chan, Phys. Rev. Letts. 88, 086101(2002)