Stick-Slip Motion and Force Fluctuations in a Driven Two-Wave Potential

A model of a particle interacting with two periodic potentials, one of which is externally driven, is analyzed. Three regimes are identified in the motion of the driven plate: (a) stick-slip motion, (b) intermittent stick slip characterized by force fluctuations, and (c) sliding which occurs above a critical driving velocity $v_c$. In the vicinity of $v_c$ the power spectra of the force obey a ${\omega }^{-2\mathrm{}}$ law and the force fluctuations decrease as $(v_c-v{)}^{1/2}$ for $v<\mathrm{}{v}_c$. Our calculations suggest that stick-slip dynamics is characterized by chaotic behavior of the top plate and the embedded molecular system. An equation is derived which provides a coarse-grained description of the plate motion near $v_c$.