Mode-Locking Hysteresis in the Globally Coupled Model of Charge-Density Waves

TL;DR

This paper investigates how global coupling affects charge-density waves under combined ac and dc drives, revealing hysteresis in mode-locking and explaining experimental asymmetries through the pinning force.

Contribution

It introduces a global coupling term into the Fukuyama-Lee-Rice model, demonstrating its effects on mode-locking hysteresis and subharmonic step behavior in charge-density waves.

Findings

Hysteresis appears on mode-locked steps due to global coupling.

Asymmetry in hysteresis size is explained by pinning force effects.

Large global coupling reduces subharmonic steps, matching experimental observations.

Abstract

We study the response of a recently proposed global coupling model of charge-density waves to a joint ac+dc drive. The model is the standard Fukuyama-Lee-Rice model with an additional global coupling term to account for interaction with (uncondensed) quasi-particles. We find that traditional mode-locking is accompanied by hysteresis on mode-locked steps. The experimentally observed asymmetry in the size of hysteresis is reproduced and explained by drawing attention to the importance of the pinning force. For large values of global coupling, increased rigidity leads to vanishing of subharmonic steps consistent with experiments.