  We investigate the influence of spatial dispersion on atom-surface quantum
friction. We show that for atom-surface separations shorter than the carrier's
mean free path within the material, the frictional force can be several orders
of magnitude larger than that predicted by local optics. In addition, when
taking into account spatial dispersion effects, we show that the commonly used
local thermal equilibrium approximation underestimates by approximately 95% the
drag force, obtained by employing the recently reported nonequilibrium
fluctuation-dissipation relation for quantum friction. Unlike the treatment
based on local optics, spatial dispersion in conjunction with corrections to
local thermal equilibrium not only change the magnitude but also the distance
scaling of quantum friction.
