Height fluctuations of a contact line: a direct measurement of the renormalized disorder correlator

Pierre Le Doussal, Kay Jörg Wiese
CNRS-Laboratoire de Physique Théorique de l'Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France.

Sebastien Moulinet, Etienne Rolley
CNRS-Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France.

Abstract

We have measured the center-of-mass fluctuations of the height of a contact line at depinning for two different systems: liquid hydrogen on a rough cesium substrate and isopropanol on a silicon wafer grafted with silanized patches. The contact line is subject to a confining quadratic well, provided by gravity. From the second cumulant of the height fluctuations, we measure the renormalized disorder correlator Δ(u), predicted by the Functional RG theory to attain a fixed point, as soon as the capillary length is large compared to the Larkin length set by the microscopic disorder. The experiments are consistent with the asymptotic form for Δ(u) predicted by Functional RG, including a linear cusp at u = 0. The observed small deviations could be used as a probe of the underlying physical processes. The third moment, as well as avalanche-size distributions are measured and compared to predictions from Functional RG.


arXiv:0904.4156 [pdf]
Phys. Rev. B 80, 144204 (2009) [pdf]


Copyright (C) by Kay Wiese. Last edited April 7, 2009.