Interface Depinning in the Absence of External Driving Force

José J. Ramasco1,2, Juan M. López3 and Miguel A. Rodríguez1
1Instituto de Física de Cantabria (CSIC-UC), Av de los Castros s/n 39005 Santander, Spain
2Dpto. de Física Moderna, Universidad de Cantabria 39005 Santander, Spain
3Dipartimento di Fisica and UnitÓ INFM, UniversitÓ di Roma "La Sapienza", I-00185 Roma, Italy

(February 2001)

We study the pinning-depinning phase transition of interfaces in the quenched Kardar-Parisi-Zhang model as the external driving force F goes towards zero. For a fixed value of the driving force we induce depinning by increasing the nonlinear term coefficient λ, which is related to lateral growth, up to a critical threshold. We focus on the case in which there is no external force applied (F=0) and find that, contrary to a simple scaling prediction, there is a finite value of λ that makes the interface to become depinned. The critical exponents at the transition are consistent with directed percolation depinning. Our results are relevant for paper wetting experiments, in which an interface gets moving with no external driving force.