Transverse ratchet effect and superconducting vortices: simulation and experiment

Abstract

A transverse ratchet effect has been measured in magnetic/superconducting hybrid films fabricated by electron beam lithography and magnetron sputtering techniques. The samples are Nb films grown on top of an array of Ni nanotriangles. Injecting an ac current parallel to the triangle reflection symmetry axis yields an output dc voltage perpendicular to the current, due to a net motion of flux vortices in the superconductor. The effect is reproduced by numerical simulations of vortices as Langevin particles with realistic parameters. Simulations provide an intuitive picture of the ratchet mechanism, revealing the fundamental role played by the random intrinsic pinning of the superconductor.

Experimental realization of smectic phase in vortex matter induced by symmetric potentials arranged in two-fold symmetry arrays

“…the applied field is a fraction or multiple of the first matching field. Note that vortex behavior is governed by the interplay between random intrinsic pinning, which is known to be strong in Nb thin films [34], and artificially induced periodic potentials [35,36]. As explained by Pogosov et al [37], under matching conditions, both these factors affect the system.…”

Ratchet Effects in Active Matter Systems

“…In geometric or drift ratchets, which require a minimum of two spatial dimensions, particles driven over an asymmetric substrate by a dc drive undergo a net dc drift in the direction transverse to the applied dc drive (9,10,11). In transverse ratchets, which are a variation of drift ratchets, a net dc ratchet motion arises in the direction transverse to an applied ac driving force (12,13,14). Additional ratchet effects including ratchet reversals can arise when there are non-dissipative terms in the equations of particle motion, such as inertia (15) or a Magnus term (16).…”

“…Studies of ratchet effects have been performed for colloids interacting with asymmetric flashing substrates (17), vortices in type-II superconductors interacting with asymmetric periodic 1D (5,6) and 2D substrates (4,12,13,14), granular matter on sawtooth substrates (18,19), cold atoms (20,21), electron systems (22,23), and domain walls moving over asymmetric substrates (24,25). These systems all require application of some form of external driving in order to create the nonequilibrium conditions necessary for a ratchet effect to occur.…”

Reversible vector ratchets for skyrmion systems

“…It is also possible to observe a transverse ratchet effect in which the net dc drift of the particles is perpendicular to applied ac drive. For such transverse ratchets, when the ac drive is applied transverse to the substrate asymmetry direction, the resulting dc drift is parallel to the substrate asymmetry in either the easy or hard flow direction 11,[16][17][18] .…”