MOBILITY OF A DRIVEN ELASTIC LATTICE IN AN INCOMMENSURATE BACKGROUND

Using Monte Carlo simulations, we study the mobility of a harmonic tri angular lattice subjected to an incommensurate short-wavelength potent ial and a steady driving force. At zero temperature (T = 0) the mobili ty jumps from zero to a finite value at a critical force F-c. For T > 0 the mobility shows Arrhenius behaviour, and grows exponentially with driving force before saturating at the free-particle limit for F > F- c. We find no evidence of a sharp depinning transition at finite tempe rature. This suggests that observations of depinning of charge-density waves, and the irreversibility line in high-temperature superconducto rs, may simply represent the onset of detectable motion on laboratory timescales, rather than an underlying phase transition.