Dynamic phases of colloidal monolayers sliding on commensurate substrates

Abstract

We report on numerical simulations of a monolayer of charge-stabilized colloids driven over a substrate potential by an external dc force acting along a symmetry axis of the monolayer. Using overdamped Langevin dynamics, we studied the sliding transition for various inter-particle interaction strengths as a function of the driving force. For weak interactions, the diffusion of individual defects is responsible for the motion of the monolayer. As the interaction strength is increased, sliding is induced by distinct density compression and decompression zones. For very strong interactions, a type of stick-slip mechanism emerges, in which the sliding of the monolayer is mediated by the propagation of collective distortion waves. Our predictions can be tested experimentally with two-dimensional arrangements of colloidal particles exposed to periodic light fields and our work shows that the inter-particle interaction strength tunes the degree of correlation in the sliding mechanism adopted by a monolayer driven over a commensurate substrate.

Dynamic regimes for driven colloidal particles on a periodic substrate at commensurate and incommensurate fillings

“…Subsequent numerical simulations of Yukawa particles interacting with egg-carton substrates at incommensurate fillings also produced kink and antikink motion, which the authors related to an effective friction [21,38]. These works showed that decreasing the substrate strength at an incommensurate filling leads to a 2D Aubry transition [46], where the depinning threshold vanishes and the colloidal lattice essentially floats on the substrate.…”

“…Experiments and computational studies have shown that in the absence of a drive, a variety of orderings can arise for colloidal particles interacting with one-dimensional (1D) periodic substrates [13,32,33], two-dimensional (2D) periodic substrates [15,20,21,[34][35][36][37][38], 2D quasiperiodic substrates [39][40][41][42][43], or 2D random substrates [44]. While these studies have provided a better understanding of several features of commensurateincommensurate behaviors, being able to dynamically control the particle ordering and dynamics could lead to a variety of applications, including self-assembled structures, particle separation, and photonic crystals.…”

Superlubric-pinned transition in sliding incommensurate colloidal monolayers

“…4,6,7,27 Colloidal monolayers in an incommensurate lattice corrugation potential are shown to represent ideal systems to study the superlubric-pinned transition, expected as a function of increasing corrugation strength, but never realized so far in any 2D system, under constant geometrical conditions. In 1D it is well known that at this transition the onset of a disorder parameter -measuring a region of phase space inaccessible to particle positions -impedes the dynamics of free-sliding motion, giving rise to static friction through a continuous phase transition.…”

“…1a). In this case a finite and large external force is required to dislodge the slider atoms from the potential minima, so as to nucleate, at finite temperature, 5,6 the onset of sliding.…”

Avalanches, plasticity, and ordering in colloidal crystals under compression

“…Additionally, there are various methods such as optical techniques 4,5 for controlling colloidal ordering and manipulating individual colloids. Examples of phenomena that have been studied with colloids include two-dimensional melting transitions 6,7 , solid-to-solid phase transitions 8 , glassy dynamics 3 , commensurate and incommensurate phases [9][10][11][12] , depinning behaviors [13][14][15][16] , self-assembly 17,18 , and dynamic sorting [19][20][21] . It is also possible to use colloids to study plastic deformation under shear in crystalline 22 or amorphous 23 colloidal assemblies.…”