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Behaviour of the current in a two-dimensional Bttiker Landauer motor with entropic barriers 下载免费PDF全文
The behaviour of the current in a two-dimensional
Büttiker--Landauer motor, which is a position-dependent
temperature-driven Brownian motor, is investigated in the presence
of entropic and energy barriers. It is found that the motion of the
Brownian particles is influenced by the shape of the channel. The
existence of an entropic barrier can cause an asymmetric current as
the flatness ratio of the shape varies. There exists an optimized
flatness ratio (nonzero) at which the current reaches its maximum
value. 相似文献
3.
Directed transport of Brownian particles in a deformable two-dimensional tube is investigated in the presence of asymmetric unbiased fluctuations. It is found that the current can be enhanced by choosing appropriate noise intensity and deformation. There exists a value of deformation at which the current takes its maximum. For small deformable parameter, transport is dominated by noise intensity, and for very large deformable parameter, transport is dominated by deformation. The competition between the deformation and the asymmetric driving forces will induce rich phenomena in transport. 相似文献
4.
Transporting velocity of a loaded Brownian motor with entropic barrier is investigated in the presence of an asymmetric unbiased force. It is found that in the presence of the entropic barrier, the stall force of the Brownian motor does not change monotonously with temperature. The average velocity of the Brownian motor is a peaked function of thermal noise and amplitude of the asymmetric unbiased external force, which indicates that a definite fluctuation can facilitate the loaded Brownian motor moving. With the increase of the load, the range of temperature and amplitude of the asymmetric unbiased external force for Brownian motor working become smaller. The limited area for Brownian motor working is given on the load-temperature plane. The threshold of fluctuation for Brownian motor working is found, and the minimum of asymmetric parameter of unbiased external force for Brownian motor working is given. 相似文献
5.
Current and efficiency of Brownian particles under oscillating forces in entropic barriers 下载免费PDF全文
In this study, considering the temporarily unbiased force and different forms of oscillating forces, we investigate the current and efficiency of Brownian particles in an entropic tube structure and present the numerically obtained results.We show that different force forms give rise to different current and efficiency profiles in different optimized parameter intervals. We find that an unbiased oscillating force and an unbiased temporal force lead to the current and efficiency,which are dependent on these parameters. We also observe that the current and efficiency caused by temporal and different oscillating forces have maximum and minimum values in different parameter intervals. We conclude that the current or efficiency can be controlled dynamically by adjusting the parameters of entropic barriers and applied force. 相似文献
6.
B.-Q. Ai H. Zheng L.-G. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(3):373-376
We study the steady state properties of an absorptive
optical bistable model in the presence of correlated noises.
Based on the corresponding Fokker-Planck equation the steady state
solution of the probability distribution and the average value of
the transmitted light have been investigated. We have found that
fluctuations of the input light amplitude improve the transmitted
light and an optimized value exists for the fluctuations of the
population difference at which the transmitted light takes its
maximum value. The correlation between the two noises reduce the
transmitted light and the noises in the model can induce a phase transition. 相似文献
7.
Transport of Brownian particles in a finite channel is investigated in the presence of asymmetric potential and an unbiased external force. It is found that the phase differencebetween the potential (energetic barriers) and the entropic barrier can break the symmetryof the system and control the transport of Brownian particles. Especially, the particlescan be pumped through the channel from a reservoir at low concentration to one at the sameor higher concentration. There exist optimized values of the parameters (the temperatureand the amplitude of the external force) at which the pumping capacity takes its maximumvalue. The pumping capacity decreases with increasing the radius at the bottleneck of thechannel. 相似文献
8.
V. Filimonov D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(5):1-5
Transport of overdamped Brownian particles in deformable potentials is investigated in the presence of asymmetrically unbiased fluctuations. It is found that the deformation of the potential can strongly affect the directed transport. For small noise strength, the current is not always monotonic function of deformable parameter. For large noise strength, there exists a value of deformable parameter at which the current takes its maximum. Therefore, it is possible to obtain the optimal transport by changing the deformation of the potential. 相似文献
9.
The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal forces.Temperature,load,and amplitude dependence of the particle current and energy conversion efficiency are investigated in three dimensions.For oscillating forces,the optimized temperature–load,amplitude–temperature,and amplitude–load intervals are determined when fixing the amplitude,load,and temperature,respectively.By using three-dimensional plots rather than two-dimensional ones,it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter regions.Furthermore,the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of forces.Finally,it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle. 相似文献
10.
S. Fugmann D. Hennig S. Martens L. Schimansky-Geier 《Physica D: Nonlinear Phenomena》2008,237(24):3179-3185
In the present paper we consider the deterministic escape dynamics of a dimer from a metastable state over an anharmonic potential barrier. The underlying dynamics is conservative and noiseless and thus, the allocated energy has to suffice for barrier crossing. The two particles comprising the dimer are coupled through a spring. Their motion takes place in a two-dimensional plane. Each of the two constituents for itself is unable to escape, but as the outcome of strongly chaotic coupled dynamics the two particles exchange energy in such a way that eventually exit from the domain of attraction may be promoted. We calculate the corresponding critical dimer configuration as the transition state and its associated activation energy vital for barrier crossing. It is found that there exists a bounded region in the parameter space where a fast escape entailed by chaotic dynamics is observed. Interestingly, outside this region the system can show Fermi resonance which, however turns out to impede fast escape. 相似文献
11.
We study the transport of overdamped Brownian particles in a symmetrically periodic potential in the presence of an asymmetrically ac driving force and a time-delayed feedback.It is found that for low frequencies,the average velocity can be negative by changing the driving amplitude,for high frequencies,there exists an optimized driving amplitude at which the average velocity takes its maximum value.Additionally,there is a threshold value of driving amplitude below which no directed transport can be obtained for high frequencies.For the large value of the delay time,the average velocity is independent of the delay time. 相似文献
12.
We report the chain dynamics in the necklace model that mimics the reptation of a chain of N particles in a two-dimensional square lattice. We focus on the drift velocity under an applied static field. The characteristics of the model allow us to determine the effects of the forces on the chains and the resulting mechanisms that affect the drift velocity. Results obtained through Monte Carlo simulations were analyzed and discussed and distinct regimes as a function of the force strength and N were identified. We found that for small total applied forces, the drift velocity scales as 1/N. When the applied force to every particle is small but the total applied force is not, the tube deforms in such a way that the drift velocity does not depend on N. Large forces, applied to every particle, can straight chains such that the distance between the chain ends increases faster than the number of particles. Also, large forces can deform the chain within the tube what is directly related to a decrease of the drift velocity. 相似文献
13.
The role of Lévy flights on fluctuation-driven transport in time independent periodic potentials with broken spatial symmetry is studied. Two complementary approaches are followed. The first one is based on a generalized Langevin model describing overdamped dynamics in a ratchet type external potential driven by Lévy white noise with stability index α in the range 1<α<2. The second approach is based on the space fractional Fokker-Planck equation describing the corresponding probability density function (PDF) of particle displacements. It is observed that, even in the absence of an external tilting force or a bias in the noise, the Lévy flights drive the system out of the thermodynamic equilibrium and generate an up-hill current (i.e., a current in the direction of the steeper side of the asymmetric potential). For small values of the noise intensity there is an optimal value of α yielding the maximum current. The direction and magnitude of the current can be manipulated by changing the Lévy noise asymmetry and the potential asymmetry. For a sharply localized initial condition, the PDF of staying at the minimum of the potential exhibits scaling behavior in time with an exponent bigger than the −1/α exponent corresponding to the force free case. 相似文献
14.
The phenomenon of entropic stochastic resonance (ESR) in a two-dimensional confined system driven by a transverse periodic force is investigated when the colored fluctuation is included in the system. Applying the method of unified colored noise approximation, the approximate Fokker-Planck equation can be derived in the absence of the periodic force. Through the escaping rate of the Brownian particle from one well to the other, the power spectral amplification can be obtained. It is found that increasing the values of the noise correlation time and the signal frequency can suppress the ESR of the system. 相似文献
15.
P. S.?Burada G.?Schmid D.?Reguera J. M.?Rubi P.?H?nggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):11-18
We demonstrate the existence of stochastic resonance (SR)
in confined systems arising from entropy variations associated to
the presence of irregular boundaries. When the motion of a Brownian
particle is constrained to a region with uneven boundaries, the
presence of a periodic input may give rise to a peak in the spectral
amplification factor and therefore to the appearance of the SR
phenomenon. We have proved that the amplification factor depends on
the shape of the region through which the particle moves and that by
adjusting its characteristic geometric parameters one may optimize
the response of the system. The situation in which the appearance of
such entropic stochastic resonance (ESR) occurs is common for
small-scale systems in which confinement and noise play an prominent
role. The novel mechanism found could thus constitute an important
tool for the characterization of these systems and can put to use
for controlling their basic properties. 相似文献
16.
Burada PS Schmid G Reguera D Vainstein MH Rubi JM Hänggi P 《Physical review letters》2008,101(13):130602
We present a novel scheme for the appearance of stochastic resonance when the dynamics of a Brownian particle takes place in a confined medium. The presence of uneven boundaries, giving rise to an entropic contribution to the potential, may upon application of a periodic driving force result in an increase of the spectral amplification at an optimum value of the ambient noise level. The entropic stochastic resonance, characteristic of small-scale systems, may constitute a useful mechanism for the manipulation and control of single molecules and nanodevices. 相似文献
17.
S. Schinzer S. Köhler G. Reents 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):161-168
We examine the step dynamics in a 1+1-dimensional model of epitaxial growth based on the BCF-theory. The model takes analytically
into account the diffusion of adatoms, an incorporation mechanism and an Ehrlich-Schwoebel barrier at step edges. We find
that the formation of mounds with a stable slope is closely related to the presence of an incorporation mechanism. We confirm
this finding using a solid-on-solid model in 2+1 dimensions. In the case of an infinite step edge barrier we are able to calculate
the saturation profile analytically. Without incorporation but with inclusion of desorption and detachment we find a critical
flux for instable growth but no slope selection. In particular, we show that the temperature dependence of the selected slope
is solely determined by the Ehrlich-Schwoebel barrier which opens a new possibility in order to measure this fundamental barrier
in experiments.
Received 11 May 1999 and Received in final form 6 November 1999 相似文献
18.
Bier M Derényi I Kostur M Astumian RD 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,59(6):6422-6432
We consider an overdamped Brownian particle in a well. When the particle escapes, it does so as an instanton, i.e., in one run and without dwelling anywhere on the way from the bottom of the well to the top of the barrier. For a sufficiently steep slope the instanton time equals the time it takes the particle to deterministically slide down the same slope. We show that the instanton time is also the relaxation time for the escape rate after the barrier changes shape. 相似文献
19.
Calculating the microscopic dissociation rate of a bound state, such as a classical diatomic molecule, has been difficult so far. The problem was that standard theories require an energy barrier over which the bound particle (or state) escapes into the preferred low-energy state. This is not the case when the long-range repulsion responsible for the barrier is either absent or screened (as in Cooper pairs, plasmas, or biomolecular complexes). We solve this classical problem by accounting for entropic driving forces at the microscopic level. The theory predicts dissociation rates for arbitrary potentials and is successfully tested on the example of plasma, where it yields an estimate of ionization in the core of the Sun in excellent agreement with experiments. In biology, the new theory accounts for crowding in receptor-ligand kinetics and protein aggregation. 相似文献
20.
We investigate Brownian pump transport in the presence of an unbiased external force. The pumping system is embedded in a
finite region bounded by two particle reservoirs. In the adiabatic limit, we obtain the analytical expressions of the current
and the concentration ratio. We find that Brownian particles can be pumped through an asymmetric potential from a particle
reservoir at low concentration to one at the same or higher concentration in the presence of an unbiased external force.
相似文献