Prewetting transition on a weakly disordered substrate: Evidence for a creeping film dynamics

Laboratoire Kastler Brossel, Ecole Normale Supérieure 24 rue Lhomond, F75231 Paris cedex 05, France

Received: 19 December 2000
Accepted: 7 March 2001

Abstract

We present the first microscopic images of the prewetting transition of a liquid film on a solid surface. Pictures of the local coverage map of a helium film on a cesium metal surface are taken while the temperature is raised through the transition. The film edge is found to advance at constant temperature by successive avalanches in a creep motion with a macroscopic correlation length. The creep velocity varies strongly in a narrow temperature range. The retreat motion is obtained only at much lower temperature, conforming to the strong hysteresis observed for prewetting transition on a disordered surface. Prewetting transition on such disordered surfaces appears to give rise to dynamical phenomena similar to what is observed for domain wall motions in 2D magnets.