Superconducting Fluxon Pumps and Lenses

Wambaugh, John F.; Reichhardt, C.; Olson, C. J.; Marchesoni, F.; Nori, Franco

doi:10.1103/physrevlett.83.5106

Cited by 235 publications

(172 citation statements)

References 39 publications

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“…This observation can be explained by noticing that, at low temperatures, the ac drive causes a moving particle to migrate to the center of the channel where it no longer interacts with the boundaries; while at high temperatures the driving force becomes irrelevant and thus the particle is no longer pushed through the channel bottlenecks periodically in time. The first simulation evidence of this phenomenon was produced by Wambaugh et al ͑1999͒. Their results obtained for the special case of magnetic vortex channeling are discussed in Sec.…”

Section: Boundary Effectsmentioning

confidence: 99%

Artificial Brownian motors: Controlling transport on the nanoscale

2009

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In systems possessing spatial or dynamical symmetry breaking, Brownian motion combined with unbiased external input signals, deterministic and random alike, can assist directed motion of particles at submicron scales. In such cases, one speaks of "Brownian motors." In this review the constructive role of Brownian motion is exemplified for various physical and technological setups, which are inspired by the cellular molecular machinery: the working principles and characteristics of stylized devices are discussed to show how fluctuations, either thermal or extrinsic, can be used to control diffusive particle transport. Recent experimental demonstrations of this concept are surveyed with particular attention to transport in artificial, i.e., nonbiological, nanopores, lithographic tracks, and optical traps, where single-particle currents were first measured. Much emphasis is given to two-and three-dimensional devices containing many interacting particles of one or more species; for this class of artificial motors, noise rectification results also from the interplay of particle Brownian motion and geometric constraints. Recently, selective control and optimization of the transport of interacting colloidal particles and magnetic vortices have been successfully achieved, thus leading to the new generation of microfluidic and superconducting devices presented here. The field has recently been enriched with impressive experimental achievements in building artificial Brownian motor devices that even operate within the quantum domain by harvesting quantum Brownian motion. Sundry akin topics include activities aimed at noise-assisted shuttling other degrees of freedom such as charge, spin, or even heat and the assembly of chemical synthetic molecular motors. This review ends with a perspective for future pathways and potential new applications.

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Section: Boundary Effectsmentioning

confidence: 99%

Artificial Brownian motors: Controlling transport on the nanoscale

2009

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“…This is the so called ratchet effect [1]. Applications to removal of trapped flux from superconductors, and to voltage rectification have been proposed [2,3,4,5,6,7]. Experimental realizations of the ratchet effect for vortices have been reported by some groups [8,9,10].…”

Section: Introductionmentioning

confidence: 99%

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Carneiro

2005

Physica C: Superconductivity

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The ratchet effect is demonstrated theoretically for the simple model of a vortex in a thin superconducting film interacting with a periodic array of magnetic dipoles placed in the vicinity of the film . The pinning potential for the vortex is calculated in the London limit and found to break spatial inversion symmetry and to depend on the orientation of the magnetic dipole moments. The motion of the vortex at zero temperature driven by a force oscillating periodically in time is investigated numerically. Drift vortex motion consisting of displacements by a translation vector of the dipole array during each period of oscillation is obtained and studied in detail. The direction of drift differs in general from that of the driving force, except if the driving force oscillates in a direction of high symmetry of the dipole array. The vortex drift velocity depends on the orientation of the magnetic moments, and can be tuned by rotating the dipoles. It is pointed out that if the magnetic moments are free to rotate, the ratchet effect can be produced and tuned by a magnetic field applied parallel to the film surfaces.

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“…In this context, several ideas to control flux motion by applying an ac excitation have been proposed [6,7,8,9], but up to now only a few experiments have been realized [10,11]. One realization has been recently implemented on a Nb film with a square array of nanoscopic triangular magnetic dots [10].…”

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Vortex-Rectification Effects in Films with Periodic Asymmetric Pinning

et al. 2005

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We study the transport of vortices excited by an ac current in an Al film with an array of nanoengineered asymmetric antidots. The vortex response to the ac current is investigated by detailed measurements of the voltage output as a function of ac current amplitude, magnetic field and temperature. The measurements revealed pronounced voltage rectification effects which are mainly characterized by the two critical depinning forces of the asymmetric potential. The shape of the net dc voltage as a function of the excitation amplitude indicates that our vortex ratchet behaves in a way very different from standard overdamped models. Rather, as demonstrated by the observed output signal, the repinning force, necessary to stop vortex motion, is considerably smaller than the depinning force, resembling the behavior of the so-called inertia ratchets. Calculations based on an underdamped ratchet model provide a very good fit to the experimental data.PACS numbers: 05.40. 74.78.Na., 74.40.+k, From the point of view of classical thermodynamics, it is not possible to induce directed motion of particles by using equilibrium fluctuations only, otherwise it would constitute a perpetuum mobile of the second kind [1]. Nevertheless, non-equilibrium fluctuations, such as periodic excitations or a "colored" noise, are allowed to take advantage of the asymmetry of a periodic ratchet potential to promote motion of particles in a preferential direction [2]. New solid-state-based ratchet systems are currently being developed for controlling the motion of electrons [3] and fluxons, as well as for particle separation [4] and electrophoresis [5]. In particular, ratchet potentials in superconducting devices may be very useful to control the dissipative motion of fluxons, which causes undesired internal noise.Modern lithographic technics make it possible to fabricate periodic arrays of vortex pinning sites with size and shape that can be easily tuned, thus giving an interesting perspective for making different asymmetric pinning potentials. In this context, several ideas to control flux motion by applying an ac excitation have been proposed [6,7,8,9], but up to now only a few experiments have been realized [10,11]. One realization has been recently implemented on a Nb film with a square array of nanoscopic triangular magnetic dots [10]. The authors reported rectification of the ac driven vortices due to the asymmetric shape of the dots. Nevertheless, the detailed dynamics of vortices in such structures is not yet completely understood.In this Letter we investigate a composite square array of pinning sites, with its unit cell consisting of a small and a big square antidot separated by a narrow superconducting wall, as a vortex rectifier. As demonstrated by our dc and ac transport measurements at several fields and temperatures, this configuration is able to break the reflection symmetry of the total effective pinning potential and promote flux quanta rectification. Moreover, our data reveals a remarkable hysteresis in the currentinduced pinni...

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Superconducting Fluxon Pumps and Lenses

Cited by 235 publications

References 39 publications

Artificial Brownian motors: Controlling transport on the nanoscale

Artificial Brownian motors: Controlling transport on the nanoscale

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Vortex-Rectification Effects in Films with Periodic Asymmetric Pinning

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