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Publications on the project |
003 003 Fluctuation-induced transport of two coupled particles: effect of the interparticle interaction. |
Authors: | Makhnovskii Yu. A., Rozenbaum V. M., Sheu S.-Y, Yang D.-Y, Trakhtenberg L. I., Lin S. H. | |
Summary: | We consider a system of two coupled particles fluctuating between two states, with different interparticle interaction potentials and particle friction coefficients. An external action drives the interstate transitions that induces reciprocating motion along the internal coordinate x (the interparticle distance). The system moves unidirectionally due to rectification of the internal motion by asymmetric friction fluctuations and thus operates as a dimeric motor that converts input energy into net movement. We focus on how the law of interaction between the particles affects the dimer transport and, in particular, the role of thermal noise in the motion inducing mechanism. It is argued that if the interaction potential behaves at large distances as x(α), depending on the value of the exponent α, the thermal noise plays a constructive (α > 2), neutral (α = 2), or destructive (α < 2) role. In the case of α = 1, corresponding piecewise linear potential profiles, an exact solution is obtained and discussed in detail. | |
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Edition: | J Chem Phys | | | 2014,
140(21):214108,English |
003 003 Symmetry Rules for Brownian Photomotors |
Authors: | Dekhtyar M. L., Rozenbaum V. М.. | |
Summary: | A number of symmetry rules have
been derived which govern the
occurrence of directed
motion and its reversals in Brownian
photomotors both for individual molecules and for
molecular ensembles. The exclusion pr
inciples and sufficient condit
ions for the photoexcited
transport of molecules ar
e found in terms of
electron density distribution symmetries in the
substrate and moving molecules. Thus, the most
general sufficient condition for a nonzero
directed velocity of a single molecule at any
symmetry type of the substrate is as follows:
symmetric or antisymmetric
components of the molecular electron
density distribution change
on excitation, the remaining symmetry componen
ts not vanishing in the ground and excited
states simultaneously. The exclusion principle for motion
reversals (
stopping points) in
single-molecule transport is such that symmet
ric and antisymmetric components of the
molecular electron density distribution change propor
tionally on excitation. For collective
molecular transport to occur, it is suffic
ient that the substrate not be symmetric and that
symmetric components of the molecular electron
density distribution not vanish in the ground
and excited states simultaneously. The
symmetry relationships established offer
much
promise for the effective quantum-chemistry base
d screening and rational molecular design of
light-driven nanodevices. | |
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Edition: | MATCH | | | 2014,
71 (2014 ) P. 609 - 626,English |
003 Adiabatic Brownian ratchets with the inclusion of inertia |
Authors: | V. M. Rozenbaum, I. V. Shapochkina, T. E. Korochkova | |
Summary: | | |
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Edition: | Journal of Experimental and Theoretical Physics Letters | | | 2013,
Т. 98. Вип. 9. с. 637-641.,Russian |
003 Adiabatically driven Brownian pumps |
Authors: | Rozenbaum V.M., Makhnovskii Yu.A., Shapochkina I.V., Sheu S.-Y., Yang D.-Y., Lin S.H. | |
Summary: | We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane. | |
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Edition: | Phys. Rev. E. | | | 2013,
V. 88, No. 1. P. 012104-1-7,English |
003 Symmetry interplay in Brownian photomotors: From a single-molecule device to ensemble transport |
Authors: | Dekhtyar M. L., Rozenbaum V. M. | |
Summary: | Unlike most of Brownian motor models in which the state of a point particle is described by a single scalar fluctuating parameter, we consider light-induced dichotomic fluctuations of electron density distributions in an extended molecule moving in the electrostatic periodic potential of a polar substrate. This model implies that the potential energy profiles of two motor states differ substantially and their symmetry is dictated by the interplay between the symmetries of the substrate potential and of molecular electronic states. As shown, a necessary condition for the occurrence of directed motion, the asymmetry of the potential energy profiles, is satisfied for (i) symmetric electron density distributions in molecules on asymmetric substrates and (ii) asymmetric electron density distributions in molecules on symmetric substrates. In the former case, the average velocity of directed motion is independent of molecular orientations and the ensemble of molecules moves as a whole, whereas in the latter case, oppositely oriented molecules move counterdirectionally thus causing the ensemble to diffuse. Using quantum chemical data for a specific organic-based photomotor as an example, we demonstrate that the behavior of molecular ensembles is controllable by switching on/off resonance laser radiation: they can be transported as a whole or separated into differently oriented molecules depending on the ratio of symmetric and antisymmetric contributions to the substrate electrostatic potential and to the molecular electron density distributions. | |
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Edition: | J. Chem. Phys. | | | 2012,
V.137, No 12. P. 124306-1-6.,English |
003 Adiabatically slow and adiabatically fast driven ratchets |
Authors: | Rozenbaum V. M., Makhnovskii Yu. A., Shapochkina I. V., Sheu S.-Y., Yang D.-Y., Lin S. H. | |
Summary: | We revisit two known models of deterministically driven ratchets, which exhibit high energetic efficiency, with the goal to uncover similarities and differences in the principles of their operation. Both the models rely on adiabaticity of the potential change process, however, the adiabaticity that we deal with in the two cases is of different types, slow and fast. It is shown that in the former (latter) case the drift velocity is an even (odd) functional of the potential, with the notable consequence that for the adiabatically slow driven ratchet the necessary symmetry breaking occurs only due to time-dependent parametric perturbations, while the spatial asymmetry of the potential is a mandatory condition for the adiabatically fast driven ratchet to operate. To treat energetic characteristics, the models are restated in terms of traveling potential ratchets. With such an approach, we find that in these cases (i) the conditions of high energetic efficiency to be reached are similar, and (ii) the symmetry properties of the kinetic coefficients are different. Based on our results, a strategy for designing efficient Brownian motors is suggested. | |
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Edition: | Phys. Rev. E. | | | 2012,
V. 85, No. 4. P. 041116-1-5.,English |
003 Quasiequilibrium directed hopping in a time-dependent two-well periodic potential |
Authors: | Rozenbaum V. M., Shapochkina I. V. | |
Summary: | We consider the directed motion of a Brownian particle in a two-well periodic potential with time-varying barriers and wells described by arbitrary periodic functions of time, v(t) and u(t), alternating with the period τ. In the framework of the low-temperature kinetic approach, we obtain explicit formulas for the probabilities of finding the particle in potential wells, average velocity of directed motion, input energy Pin and useful work Pout against additionally introduced stationary load force f. These formulas are considerably simplified by the assumption of the quasiequilibrium regime of motion corresponding to small values of u(t) and f. It is shown that depending on the same or opposite parity of the functions v(t) and u(t) with respect to time reversal, the motion direction of a Brownian particle is retained or reversed under the reversal of the direction of movement along the (v−u) loop in the phase space of the functions v(t) and u(t), and the nondiagonal kinetic coefficients are mutually symmetric or antisymmetric. In the adiabatic limit τ→∞, the average velocity is proportional to τ−1 in two cases: (i) the above loop has a nonzero area, (ii) the functions v(t) and u(t) are proportional to each other (zero loop area) and include intervals of fast changes with small durations τ0 on the period τ of their variations. In both of these cases, the efficiency of energy conversion, η=Pout/Pin, tends to unity at large variations of the barriers v(t). In the second case, the deviation of η from unity can be split into two contributions: The former decreases exponentially with increasing amplitude v0 of v(t), while the latter is a small nonadiabatic correction proportional to v−3/20. It is the nonadiabatic correction that limits high efficiencies at large variations of barriers. | |
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Edition: | Phys. Rev. E. | | | 2011,
V. 84, No.5, P. 051101-1-12.,English |
003 Two-state Brownian motor driven by synchronously fluctuating unbiased forces |
Authors: | Rozenbaum V. M., Makhnovskii Yu. A., Sheu S.-Y., Yang D.-Y., Lin S. H. | |
Summary: | As a model of the Brownian motor, we consider a particle moving unidirectionally under the action of two synchronously fluctuating unbiased forces, transverse and longitudinal with respect to the particle track. The former force induces track-normal transitions of the particle between the attached and detached states (with and without a periodic potential, respectively), whereas the latter drives track-parallel motion in either state. Analytical expressions of the current and efficiency are derived for different regimes, with due account of the delayed response of the system to force fluctuations. For a sawtooth potential in the attached state, we reveal several motion regimes affording the maximum current or the maximum efficiency. A special emphasis is placed on the possibility of current reversal. As shown, the interplay between two phase-shifted harmonically varied forces as well as inherent and externally induced asymmetry can lead to the emergence of multiple current reversals, thus enabling the flexible controllability of the motion direction. | |
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Edition: | Phys. Rev. E. | | | 2011,
V. 84, No.2, P. 021104-1-8.,English |
003 Brownian motor with competing spatial and temporal asymmetry of potential energy |
Authors: | Rozenbaum V. M. Korochkova T. Ye., Chernova A. A., Dekhtyar M. L. | |
Summary: | A Brownian motor is considered which operates due to asymmetric dichotomic fluctuations of the spatially periodic asymmetric potential energy. As shown, the motion direction and stopping points of this motor are dictated by the competition between the spatial and temporal asymmetry of the potential energy (or solely by temporal asymmetry in the case that the potential energy sign fluctuates). For an asymmetric sawtooth potential, the Brownian-particle average velocity is calculated numerically as a function of certain parameters of the model, whereas the low-frequency and low-energy approximations allow the corresponding analytical relationships to be derived for an arbitrarily shaped potential profile. It is shown that temporal asymmetry is not necessary for stopping point occurrence provided that the potential profile fluctuates not only in amplitude but in shape as well. This inference is illustrated by photoinduced fluctuations of the potential energy for a number of substituted arylpyrene molecules on a substrate with symmetrically distributed charge density. | |
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Edition: | Phys. Rev. E. | | | 2011,
V. 83, No.5, P. 051120-1-10,English |
The events in the framework of the project |
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003 1.1. Nanophysics: fundamental problems Purpose: Expected results:Issue of new types of products: methods, theories Stage 1:Створення теорії броунівських моторів, що описує вплив конкуренції просторової і часової асиметрії потенціальної енергії, що зазнає дихотомних флуктуацій, на напрямок руху, середню швидкість і точки зупинки мотора. Вивчення впливу розподілу заряду молекули, флуктуюючої під дією резонансного лазерного випромінювання, на її середню швидкість руху уздовж різних полярних підкладок. Stage 2:Розробка наближених аналітичних та чисельних методів розрахунку швидкості направленого руху наночастинок поблизу границі розділу фаз. Вивчення впливу симетрії розподілу заряду підкладки і молекули на швидкість її руху вздовж підкладки при флуктуаціях резонансного лазерного випромінювання. Stage 3:Вивчення моделей броунівських моторів і насосів з потенціальним рельєфом, що зсовується, які є перспективними для високоефективного перетворення енергії флуктуацій в корисну роботу. Дослідження здатності молекулярного насосу з флуктуаціями потенціалу всередині мембрани до підтримання заданої концентрації носіїв по обидві сторони мембрани. Stage 4:Вивчення колективного направленого транспорту наночастинок вздовж підкладки, індукованого циклічним процесом їх фотозбудження. Stage 5:Вивчення залежності характеристик двочастинкових броунівських моторів від типу взаємодії між наночастинками.
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