  In a pioneer experiment, Bohlein et al. realized the controlled sliding of
two-dimensional colloidal crystals over laser-generated periodic or
quasi-periodic potentials. Here we present realistic simulations and arguments
which besides reproducing the main experimentally observed features, give a
first theoretical demonstration of the potential impact of colloid sliding in
nanotribology. The free motion of solitons and antisolitons in the sliding of
hard incommensurate crystals is contrasted with the soliton-antisoliton pair
nucleation at the large static friction threshold Fs when the two lattices are
commensurate and pinned. The frictional work directly extracted from particles'
velocities can be analysed as a function of classic tribological parameters,
including speed, spacing and amplitude of the periodic potential (representing
respectively the mismatch of the sliding interface, and the corrugation, or
"load"). These and other features suggestive of further experiments and
insights promote colloid sliding to a novel friction study instrument.
