Continuous and Discontinuous Transitions in the Depinning of Two-Dimensional Dusty Plasmas on a One-Dimensional Periodic Substrate

TL;DR

This study uses Langevin simulations to explore how two-dimensional dusty plasmas transition between pinned, disordered, and ordered states on a one-dimensional substrate, revealing how substrate depth influences the nature of phase transitions.

Contribution

It demonstrates how substrate depth modulates the depinning phase transition, identifying continuous and discontinuous transitions and hysteresis effects in dusty plasmas.

Findings

Shallow substrates exhibit two continuous phase transitions.

Deeper substrates show a change to discontinuous transitions.

Hysteresis observed in the collective drift velocity.

Abstract

Langevin dynamical simulations are performed to study the depinning dynamics of two-dimensional dusty plasmas on a one-dimensional periodic substrate. From the diagnostics of the sixfold coordinated particles $P_6$ and the collective drift velocity $V_x$, three different states appear, which are the pinning, disordered plastic flow, and moving ordered states. It is found that the depth of the substrate is able to modulate the properties of the depinning phase transition, based on the results of $P_6$ and $V_x$, as well as the observation of hysteresis of $V_x$ while increasing and decreasing the driving force monotonically. When the depth of the substrate is shallow, there are two continuous phase transitions. When the potential well depth slightly increases, the phase transition from the pinned to the disordered plastic flow states is continuous; however, the phase transition from the disordered plastic flow to the moving ordered states is discontinuous. When the substrate is even deeper, the phase transition from the pinned to the disordered plastic flow states changes to discontinuous. When the substrate further increases, as the driving force increases, the pinned state changes to the moving ordered state directly, so that the disordered plastic flow state disappears completely.