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 upsilon(c). In the vicinity of upsilon(c) the power spectra of the force obey a omega(-2) law and the force fluctuations decrease as (upsilon(c) - upsilon)(1/2) for upsilon < upsilon(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 upsilon(c).