Interacting particles in disordered flashing ratchets

Chacko, Jim; Tripathy, Goutam

doi:10.1007/s12648-015-0660-5

Cited by 5 publications

(3 citation statements)

References 44 publications

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“…Here, we identify two parameters, the shape of the potential and the amount of friction on the electron (defined as the ratio of the potential oscillation timescale to the electron relaxation timescale), that, when explored simultaneously over a large parameter space, reveal two modes of ratchet operation that produce current by two different mechanisms. Prior work that explored the effect of shape on the behavior of the ratchet current focused on variations to a single potential [28][29][30][31][32][33][34]; however, while the current from a ratchet of a single shape does show resonances at certain oscillation frequencies [20], examining the frequency dependence of a single shape does not make apparent the transition from under-damped to over-damped ratcheting mechanisms. Identifying this transition, which is only possible when considering the complete space of biharmonic shapes and a large range of friction values, is critical in uncovering physically intuitive behaviors, and relating these behaviors to structural features of this complex system.…”

Section: Introductionmentioning

confidence: 99%

Identification of two mechanisms for current production in a biharmonic flashing electron ratchet

et al. 2016

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Ratchets rectify the motion of randomly moving particles, which are driven by isotropic sources of energy such as thermal and chemical energy, without applying a net, time-averaged force between source and drain. This paper describes the behavior of a damped electron, modeled by a quantum Lindblad master equation, within a flashing ratchet (a one-dimensional potential that oscillates between a flat surface and a periodic asymmetric surface). By examining the complete space of all biharmonic potential shapes and a large range of oscillation frequencies, two modes of ratchet operation, differentiated by their oscillation frequencies (relative to the rate of electron relaxation), are identified. Slow-oscillating, strong friction ratchets operate by a classical, overdamped mechanism. In fast-oscillating, weak friction ratchets, current is primarily produced when the frequency of the oscillating potential is resonant with the beating of the electron wave function in the potential well. The shape of the ratchet potential determines the direction of the current (and, in some cases, straightforwardly accounts for current reversals), but the maximum achievable current at any shape is controlled by the degree of friction applied to the electron.

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Section: Introductionmentioning

confidence: 99%

Identification of two mechanisms for current production in a biharmonic flashing electron ratchet

et al. 2016

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“…Several previous theoretical studies reveal a strong dependence of ratchet behavior on the density of repelling particles, specifically, single − or multipeaked , (including reversals of current polarity) dependence of ratchet current on particle density. Additionally, Nitzan and co-workers explored the ratcheting of interacting particles on a discrete-site chain and identified at least one regime where ratchet efficiency increases with increasing density of repulsive particles .…”

Section: Introductionmentioning

confidence: 93%

Cooperative Transport in a Multi-Particle, Multi-Dimensional Flashing Ratchet

Kedem

Weiss

2019

J. Phys. Chem. C

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Random and undirected forces are rectified in biological and synthetic systems using ratcheting mechanisms, which employ periodic asymmetric potentials and nonequilibrium conditions to produce useful transport. The density of motors or transported particles is known to strongly affect the nature and efficacy of transport in biological systems, as well as in synthetic ratchets and active swimmer systems. While experimental ratchet implementations typically employ potentials varying in two dimensions (2D), the role of the density of interacting particles in such a system has not been modeled. Prompted by experimental observations and building upon previous simulations, this paper describes the ratcheting process of interacting particles in a 2D flashing ratchet, studied using classical simulations. Increased particle density is found to allow effective ratcheting at higher driving frequencies, compared to the low-density or non-interacting case. High densities also produce a new ratcheting mode at low driving frequencies, based on independent trajectories of high kinetic-energy particles, more than doubling transport at low frequencies.

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“…A second major feature of a ratchet is the dependence of ratchet current on the density and interaction potential of ratchet particles. Theoretical studies of repulsively interacting particles (e.g., hard sphere − and Coulombic repulsion) have revealed a strong dependence of the ratchet current on particle density, identifying regimes of cooperative transport and destructive particle jamming, but there have been no experimental studies of the relationship of the frequency response and the carrier density for a particular type of transport layer.…”

Section: Introductionmentioning

confidence: 99%

Empirical Mappings of the Frequency Response of an Electron Ratchet to the Characteristics of the Polymer Transport Layer

Kodaimati¹,

Kedem²,

Schatz

et al. 2019

J. Phys. Chem. C

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Flashing electron ratchets oscillate a periodic asymmetric potential to rectify nondirectional forces and thereby produce directional transport of electrons with zero source-drain bias. The relationship between the oscillation frequency of the potential and the ratchet (short-circuit) current reflects microscopic mechanisms of charge transport within the device. This paper describes experimental mappings of the “optimal frequency(ies)” of the ratchet f peakthe oscillation frequencies that produce the largest ratchet currentto the carrier concentration, n h, and to the linear field effect transistor mobility, μh, for a poly(3-hexylthiophene-2,5-diyl) (P3HT) transport layer. Measurements on multiple devices, multiple P3HT films per device, and a range of annealing and photoexcitation conditions yield the empirical relationships f peak ∝ n h and f peak ∝ μh 2/3. Finite-element simulations suggest the sublinear relationship between mobility and peak frequency arises due to a combination of damped and inertial motion of the holes. This work also provides evidence that the frequency response of ratchets is sensitive to multiple length scales of asymmetry encoded within the periodic electrical potential. These multiple asymmetries cause changes in the polarity of the ratchet current at points within the frequency response, a long-mysterious characteristic of particle ratchets called “current inversion”, by encouraging transport in opposite directions in different frequency regimes.

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Interacting particles in disordered flashing ratchets

Cited by 5 publications

References 44 publications

Identification of two mechanisms for current production in a biharmonic flashing electron ratchet

Identification of two mechanisms for current production in a biharmonic flashing electron ratchet

Cooperative Transport in a Multi-Particle, Multi-Dimensional Flashing Ratchet

Empirical Mappings of the Frequency Response of an Electron Ratchet to the Characteristics of the Polymer Transport Layer

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