  Using numerical simulations we study the pinning and dynamics of interacting
colloids on periodic one-dimensional substrates. As a function of colloid
density, temperature, and substrate strength, we find a variety of pinned and
dynamic states including pinned smectic, pinned buckled, two-phase flow, and
moving partially ordered structures. We show that for increasing colloid
density, peaks in the depinning threshold occur at commensurate states. The
scaling of the pinning threshold versus substrate strength changes when the
colloids undergo a transition from one-dimensional chains to a buckled
configuration.
