  The sliding friction of a dimer moving over a periodic substrate and
subjected to an external force is studied in the steady state for arbitrary
temperatures within a one-dimensional model. Nonlinear phenomena that emerge
include dynamic bistability and hysteresis, and can be related to earlier
observations for extended systems such as the Frenkel-Kontorova model. Several
observed features can be satisfactorily explained in terms of the resonance of
a driven-damped nonlinear oscillator. Increasing temperature tends to lower the
resonant peak and wash out the hysteresis.
