  Using Brownian dynamics (BD) simulations and an analytical approach we
investigate the shear-induced, nonequilibrium dynamics of dense colloidal
suspensions confined to a narrow slit-pore. Focusing on situations where the
colloids arrange in well-defined layers with solidlike in-plane structure, the
confined films display complex, nonlinear behavior such as collective depinning
and local transport via density excitations. These phenomena are reminiscent of
colloidal monolayers driven over a periodic substrate potential. In order to
deepen this connection, we present an effective model which maps the dynamics
of the shear-driven colloidal layers to the motion of a single particle driven
over an effective substrate potential. This model allows to estimate the
critical shear rate of the depinning transition based on the equilibrium
configuration, revealing the impact of important parameters such as the
slit-pore width and the interaction strength. We then turn to heterogeneous
systems where a layer of small colloids is sheared with respect to bottom
layers of large particles. For these incommensurate systems we find that the
particle transport is dominated by density excitations resembling the so-called
"kink" solutions of the Frenkel-Kontorova (FK) model. In contrast to the FK
model, however, the corresponding "antikinks" do not move.
