MODE-LOCKING HYSTERESIS IN THE GLOBALLY COUPLED MODEL OF CHARGE-DENSITY WAVES

We study the response of a recently proposed global-coupling model of charge-density waves to a joint ac plus dc drive. The model is the sta ndard Fukuyama-Lee-Rice model with an additional global-coupling term to account for interaction with (uncondensed) quasiparticles. We find that traditional mode locking is accompanied by hysteresis on mode-loc ked steps. The experimentally observed asymmetry in the size of hyster esis is reproduced and explained by drawing attention to the importanc e of the pinning force. For large values of global coupling, low-dimen sional behavior leads to vanishing of subharmonic steps consistent wit h experiments.