Stochastic theory of non-equilibrium wetting

– We study a Langevin equation describing non-equilibrium depinning and wetting transitions. Attention is focused on short-ranged attractive substrate-interface potentials. We confirm the existence of first-order depinning transitions, in the temperature-chemical potential diagram, and a tricritical point beyond which the transition becomes a non-equilibrium complete wetting transition. The coexistence of pinned and depinned interfaces occurs over a finite area, in line with other non-equilibrium systems that exhibit first-order transitions. In addition, we find two types of phase coexistence, one of which is characterized by spatio-temporal intermittency (STI). A finite-size analysis of the depinning time is used to characterize the different coexisting regimes. Finally, a stationary distribution of characteristic triangles or facets was shown to be responsible for the structure of the STI phase. Consider a bulk phase (α) in contact with a substrate. Wetting occurs when a macroscopic layer of a different, coexisting, bulk phase (β) is adsorbed at the substrate. The wetting transition is characterized by the divergence of the wetting layer thickness, i.e. the distance between the substrate and the αβ interface. Equilibrium wetting is a problem of outmost importance. It has been observed experimentally and thoroughly investigated using (among other techniques) interface displacement models [1]. In these models one considers a function h(x) representing the local departure of the interface from a reference plane (h = 0) and constructs an effective interface Hamiltonian, H(h). Using reasonable approximations one arrives at the standard form [1],