We introduce a simple model consisting of two or three coupled one-dimensional channels of particles with Yukawa interactions. For the two channel system, when an external drive is applied only to the top or primary channel, we find a transition from locked flow where particles in both channels move together to decoupled flow where the particles in the secondary or undriven channel move at a slower velocity than the particles in the primary or driven channel. Pronounced commensurability effects in the decoupling transition occur when the ratio of the number of particles in the top and bottom channels is varied, and the coupling of the two channels is enhanced when this ratio is an integer or a rational fraction. Near the commensurate fillings, we find additional features in the velocity-force curves caused by the slipping of individual vacancies or incommensurations in the secondary channels. For three coupled channels, when only the top channel is driven we find a remarkably rich variety of distinct dynamic phases, including multiple decoupling and recoupling transitions. These transitions produce pronounced signatures in the velocity response of each channel. We also find regimes where a negative drag effect can be induced in one of the non-driven channels. The particles in this channel move in the opposite direction from the particles in the driven channel due to the mixing of the two different periodic frequencies produced by the discrete motion of the particles in the two other channels. In the two channel system, we also demonstrate a ratchet effect for the particles in the secondary channel when an asymmetric drive is applied to the primary channel. This ratchet effect is similar to that observed in superconducting vortex systems when there is a coupling between two different species of vortices.

Abstract. -We consider a simple model for examining the effects of quenched disorder on drag consisting of particles interacting via a Yukawa potential that are placed in two coupled onedimensional channels. The particles in one channel are driven and experience a drag from the undriven particles in the second channel. In the absence of pinning, for a finite driving force there is no pinned phase; instead, there are two dynamical regimes of completely coupled or locked flow and partially coupled flow. When pinning is added to one or both channels, we find that a remarkably rich variety of dynamical phases and drag effects arise that can be clearly identified by features in the velocity force curves. The presence of quenched disorder in only the undriven channel can induce a pinned phase in both channels. Above the depinning transition, the drag on the driven particles decreases with increasing pinning strength, and for high enough pinning strength, the particles in the undriven channel reach a reentrant pinned phase which produces a complete decoupling of the channels. We map out the dynamic phase diagrams as a function of pinning strength and the density of pinning in each channel. Our results may be relevant for understanding drag coupling in 1D Wigner crystal phases, and the effects we observe could also be explored using colloids in coupled channels produced with optical arrays, vortices in nanostructured superconductors, or other layered systems where drag effects arise.There are many examples of one-and two-dimensional (1D and 2D) coupled bilayers or coupled channels of interacting particles, including vortices in superconducting bilayers [1,2], colloidal systems [3-6], dusty plasmas [7], and Wigner crystals [8][9][10]. In many of these systems it is possible to apply an external drive to one of the layers and measure the resulting response of the other layer as well as the drag effect produced by the particles in the undriven layer on those in the driven layer. For instance, this type of measurement has been performed for the transformer geometry in two-layer superconducting vortex systems [1,2]. If the vortices in each layer are completely coupled, the measured response is the same in both layers. If instead the vortices are only partially coupled between layers, the response is reduced in the undriven layer compared to the driven layer. A similar coupling-decoupling transition is also predicted for coupled wires containing 1D Wigner crystals [8], and certain drag effects in 1D wires have been interpreted as resulting from the formation of 1D Wigner crystal states [9].Many of these systems can contain some form of quenched disorder which could produce pinning effects [11]; however, very little is known about how pinning alters the drag or transport properties in layered geometries. The quenched disorder could be strong in one channel and weak in another, or it could be of equal strength in both channels, resulting in different types of dynamic phases. Particles driven over random quenched disorder in sin...