  The far-from-equilibrium dynamics of two crystalline two-dimensional
monolayers driven past each other is studied using Brownian dynamics
simulations. While at very high and low driving rates the layers slide past one
another retaining their crystalline order, for intermediate range of drives the
system alternates irregularly between the crystalline and fluid-like phases. A
dynamical phase diagram in the space of interlayer coupling and drive is
obtained. A qualitative understanding of this stochastic alternation between
the liquid-like and crystalline phases is proposed in terms of a reduced model
within which it can be understood as a stochastic resonance for the dynamics of
collective order parameter variables. This remarkable example of stochastic
resonance in a spatially extended system should be seen in experiments which we
propose in the paper.
