  Long-range interactions often proceed as a sequence of hopping through
intermediate, statistically-favored events. Here, we identify a
widely-overlooked mechanism for the mechanical motion of particles that arises
from the Lorentz force and plasmon radiation. Even if the radiation is weak,
the nonconservative Lorentz force produces stable locations perpendicular to
the plasmon oscillation; over time, distinct patterns emerge. Experimentally,
linearly-polarized light leads to the formation of 80-nm Au nanoparticles,
perpendicularly-aligned, with lengths that are orders of magnitude greater than
their plasmon near-field interaction. There is a critical intensity threshold
and optimal concentration for observing self-assembly.
