159 research outputs found
Subdiffusion via dynamical localization induced by thermal equilibrium fluctuations
We reveal the mechanism of subdiffusion which emerges in a straightforward,
one dimensional classical nonequilibrium dynamics of a Brownian ratchet driven
by both a time-periodic force and Gaussian white noise. In a tailored parameter
set for which the deterministic counterpart is in a non-chaotic regime,
subdiffusion is a long-living transient whose lifetime can be many, many orders
of magnitude larger than characteristic time scales of the setup thus being
amenable to experimental observations. As a reason for this subdiffusive
behaviour in the coordinate space we identify thermal noise induced dynamical
localization in the velocity (momentum) space. This novel idea is distinct from
existing knowledge and has never been reported for any classical or quantum
systems. It suggests reconsideration of generally accepted opinion that
subdiffusion is due to road distributions or strong correlations which reflect
disorder, trapping, viscoelasticity of the medium or geometrical constraints.Comment: in press in Scientific Reports (2017
Efficiency of the SQUID Ratchet Driven by External Current
We study theoretically the efficiency of an asymmetric superconducting
quantum interference device (SQUID) which is constructed as a loop with three
capacitively and resistively shunted Josephson junctions. Two junctions are
placed in series in one arm and the remaining one is located in the other arm.
The SQUID is threaded by an external magnetic flux and driven by an external
current of both constant (dc) and time periodic (ac) components. This system
acts as a nonequilibrium ratchet for the dc voltage across the SQUID with the
external current as a source of energy. We analyze the power delivered by the
external current and find that it strongly depends on thermal noise and the
external magnetic flux. We explore a space of the system parameters to reveal a
set for which the SQUID efficiency is globally maximal. We detect the
intriguing feature of the thermal noise enhanced efficiency and show how the
efficiency of the device can be tuned by tailoring the external magnetic flux.Comment: accepted for publication in New Journal of Physic
Absolute negative mobility induced by white Poissonian noise
We research the transport properties of inertial Brownian particles which
move in a symmetric periodic potential and are subjected to both a symmetric,
unbiased time-periodic external force and biased Poissonian white shot noise
(of non-zero average F) being composed of a random sequence of delta-shaped
pulses with random amplitudes. Upon varying the parameters of white shot-noise
one conveniently can manipulate the transport direction and the overall
nonlinear response behavior. Within tailored parameter regimes, we find that
the response is opposite to the applied average bias F of such white shot
noise. This very transport characteristics thus mimics a nonlinear Absolute
Negative Mobility (ANM) regime. Moreover, such white shot noise driven ANM is
robust with respect to statistics of the shot noise spikes. Our findings can be
checked and corroborated experimentally by use of a setup that consists of a
single resistively and capacitively shunted Josephson junction device.Comment: 14 pages, 12 figures; accepted in J. Stat. Mech.: Theor. Exp. (2013
Coexistence of absolute negative mobility and anomalous diffusion
Using extensive numerical studies we demonstrate that absolute negative
mobility of a Brownian particle (i.e. the net motion into the direction
opposite to a constant biasing force acting around zero bias) does coexist with
anomalous diffusion. The latter is characterized in terms of a nonlinear
scaling with time of the mean-square deviation of the particle position. Such
anomalous diffusion covers "coherent" motion (i.e. the position dynamics x(t)
approaches in evolving time a constant dispersion), ballistic diffusion,
subdiffusion, superdiffusion and hyperdiffusion. In providing evidence for this
coexistence we consider a paradigmatic model of an inertial Brownian particle
moving in a one-dimensional symmetric periodic potential being driven by both
an unbiased time-periodic force and a constant bias. This very setup allows for
various sorts of different physical realizations
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