Inertial Brownian motors driven by biharmonic signals

Transport properties of two coupled Josephson junctions driven by ac currents and thermal fluctuations are studied with the purpose of determining dc voltage characteristics. It is a physical realization of directed transport induced by a non-biased zero averaged external signal. The ac current is applied either to (A) only one junction as a biharmonic current or (B) is split into two simple harmonic components and separately applied to respective junctions. We identify regimes where junctions can operate with the same as well as opposite signs of voltages. A general observation is that in the same parameters regimes, the scenario (B) is more efficient in the sense that the induced dc voltages take greater values.

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“…We consider two scenarions. In the first scenario (A), the ac driving to applied to only one of the junctions [15,17], namely,…”

Section: External Current Drivingmentioning

confidence: 99%

“…The influence of the unbiased biharmonic ac current on a single junction has been considered in Refs. [15]. Recently the dynamics of the phase difference of coupled junctions has been addressed [16,17].…”

Section: Introductionmentioning

confidence: 99%

Directed transport in coupled noisy Josephson junctions controlled via ac signals

Machura¹,

Spiechowicz²,

Łuczka³

2012

Phys. Scr.

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“…The appearance of a ratchet effect, that is, the generation of directed motion, in such a setup is very well established [17][18][19][20][21][22].…”

Section: A Ratchet Setupmentioning

confidence: 99%

Current reversals in a rocking ratchet: The frequency domain

et al. 2011

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Motivated by recent work [D. Cubero et al., Phys. Rev. E 82, 041116 (2010)], we examine the mechanisms which determine current reversals in rocking ratchets as observed when varying the frequency of the drive. We found that a class of these current reversals in the frequency domain is precisely determined by dissipation-induced symmetry breaking. Our experimental and theoretical work thus extends and generalizes the previously identified relationship between dynamical and symmetry-breaking mechanisms in the generation of current reversals.

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confidence: 99%

“…Josephson ratchets based on asymmetry of the drive rather than the potential itself have also been realized [13,14]. The nonlinear signal mixing of two driving forces was also shown to be capable to control transport in different deterministic and Brownian ratchet devices [15,16].In this Letter, we propose a ratchet based on an inhomogeneous phase change along the planar JJ. The simplest practical realization of such phase distribution can be realized by pinning an Abrikosov vortex (AV) nearby the junction (see Fig.…”

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confidence: 99%

Rectification by an Imprinted Phase in a Josephson Junction

et al. 2011

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A Josephson phase shift can be induced in a Josephson junction by a strategically nearby pinned Abrikosov vortex (AV). For an asymmetric distribution of imprinted phase along the junction (controlled by the position of the AV) such a simple system is capable of rectification of ac current in a broad and tunable frequency range. The resulting rectified voltage is a consequence of the directed motion of a Josephson antivortex which forms a pair with the AV when at local equilibrium. The proposed realization of the ratchet potential by imprinted phase is more efficient than the asymmetric geometry of the junction itself, it is easily realizable experimentally, and provides rectification even in the absence of applied magnetic field.PACS numbers: 74.50.+r,74.45.+c, 74.78.Na, 74.25.Fy, 74.20.De Starting from the discovery of biological molecular motors [1], the ratchet effect has been demonstrated in many different physical systems, where rectification in the presence of external random or periodic forces with zero time average is induced by means of spatial or temporal asymmetries (see Ref.[2] for a review). Among other solid-state ratchet systems, superconducting ratchets have been realized -based on Abrikosov vortices [3]. Josephson vortex ratchets were also studied, in long Josephson junctions (JJs) [4][5][6] and in specially engineered JJ arrays [7]. Voltage rectification based on the Josephson phase change has been demonstrated in asymmetric [8,9] and three-junction SQUIDs [10,11], and in annular JJs [12] with the asymmetric potential created by junction design, by inhomogeneous magnetic field [5] or by extra current biasing [6]. Josephson ratchets based on asymmetry of the drive rather than the potential itself have also been realized [13,14]. The nonlinear signal mixing of two driving forces was also shown to be capable to control transport in different deterministic and Brownian ratchet devices [15,16].In this Letter, we propose a ratchet based on an inhomogeneous phase change along the planar JJ. The simplest practical realization of such phase distribution can be realized by pinning an Abrikosov vortex (AV) nearby the junction (see Fig. 1). An AV can be inserted into the sample, e.g., by field cooling [17], or by passing a large bias current through the system [18]. Once in the system, the location of the AV can be controlled by e.g. appropriately directed transport current [17]. However, such current would affect the JJ as well. A more elegant way of nucleating, as well as manipulating the AV is through the use of an electron beam, demonstrated experimentally by Ustinov et al. [19]. Here, we keep the AV from penetrating into the junction, since its magnetic field is known to strongly alter the properties of the junction [20].Our idea is fairly simple. In the presence of an applied ac current, an off-center location of the AV creates an asymmetric phase imprint on the junction and, consequently, an asymmetric potential for the motion of a Josephson fluxon along the junction. This in turn generates a net...

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Inertial Brownian motors driven by biharmonic signals

Cited by 24 publications

References 31 publications

Directed transport in coupled noisy Josephson junctions controlled via ac signals

Directed transport in coupled noisy Josephson junctions controlled via ac signals

Current reversals in a rocking ratchet: The frequency domain

Rectification by an Imprinted Phase in a Josephson Junction

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