Controlled multiple reversals of a ratchet effect

Abstract

A single particle confined in an asymmetric potential demonstrates an anticipated ratchet effect by drifting along the 'easy' ratchet direction when subjected to non-equilibrium fluctuations. This well-known effect can, however, be dramatically changed if the potential captures several interacting particles. Here we demonstrate that the inter-particle interactions in a chain of repelling particles captured by a ratchet potential can, in a controllable way, lead to multiple drift reversals, with the drift sign alternating from positive to negative as the number of particles per ratchet period changes from odd to even. To demonstrate experimentally the validity of this very general prediction, we performed transport measurements on a.c.-driven vortices trapped in a superconductor by an array of nanometre-scale asymmetric traps. We found that the direction of the vortex drift does undergo multiple reversals as the vortex density is increased, in excellent agreement with the model predictions. This drastic change in the drift behaviour between single- and multi-particle systems can shed some light on the different behaviour of ratchets and biomembranes in two drift regimes: diluted (single particles) and concentrated (interacting particles).

Magnetic field tunable vortex diode made of YBa2Cu3O7−δ Josephson junction asymmetrical arrays

“…7-12) and realized. [13][14][15][16][17][18][19] It is important to stress that a significant feature of the fluxtronic devices is their great tunability as compared to their electronic counterparts, for instance, the vortex diode fabricated and tested in Ref. 13 allows the direction of rectification to be reversed simply by tuning the applied B.…”

Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

“…the topological excitations (vortices) are frequently subjected to stratified conditions [1][2][3][4]. In practice such vortices also often satisfy some confinement conditions due to finite sizes of the systems.…”

Two-dimensional optical thermal ratchets based on Fibonacci spirals

“…(11) through (15). Collisions arising in more highly occupied patterns could give rise to additional transport phenomena such as cooperative flux reversal of the type that is observed in ratchets for magnetic flux quanta [43,44] and bacterial swarms [45]. This is a matter for future study.…”