Volume 87, Number 5, September 2009
Article Number 56001
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 16 September 2009
EPL, 87 (2009) 56001
DOI: 10.1209/0295-5075/87/56001

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

P. Le Doussal1, K. J. Wiese1, S. Moulinet2, 3 and E. Rolley2

1   CNRS-Laboratoire de Physique Théorique de l'Ecole Normale Supérieure - 24 rue Lhomond, 75005 Paris, France, EU
2   Laboratoire de Physique Statistique, (ENS, CNRS, Universités Paris 6 et Paris 7) - 24 rue Lhomond, 75005 Paris, France, EU
3   Laboratoire Jean Perrin (CNRS, Université Paris 6) - 24 rue Lhomond, 75005 Paris, France, EU

received 29 April 2009; accepted in final form 18 August 2009; published September 2009
published online 16 September 2009

We measure 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 $\Delta (u)$, predicted by Functional RG 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 $\Delta (u)$ 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.

68.35.Rh - Phase transitions and critical phenomena.

© EPLA 2009