共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Fledderjohann K.-H. Mütter 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):211-218
We investigate the influence of energetic disorder, viscous damping and an external field on the electron transfer (ET) in
DNA. The double helix structure of the λ-form of DNA is modeled by a steric oscillator network. In the context of the base-pair
picture two different kinds of modes representing twist motions of the base pairs and H-bond distortions are coupled to the
electron amplitude. Through the nonlinear interaction between the electronic and the vibrational degrees of freedom localized
stationary states in the form of standing electron-vibron breathers are produced which we derive with a stationary map method.
We show that in the presence of additional energetic disorder the degree of localization of such breathers is enhanced. It
is demonstrated how an applied electric field initiates the long-range coherent motion of breathers along the bases of a DNA
strand. These moving electron-vibron breathers, absorbing energy from the applied field, sustain energetic losses due to the
viscous friction caused by the aqueous solvent as well as the impact of a moderate amount of energetic disorder. Moreover,
it is illustrated that with the choice of the amplitude and frequency of the external field, the breather can be steered to
a desired lattice position achieving control of the ET.
Received 5 July 2002 Published online 29 November 2002 相似文献
2.
G.H. Zhou Q.L. Xia J.R. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):297-304
The nonlinear localized vibrational modes of a one-dimensional atomic chain with two periodically alternating masses and force
constants are analytically investigated using a discrete multiple-scale expansion method. This model simulates a row of atoms
in the <1 1 1>-direction of sphalerite, or zinc blende, crystals. Owing to the structural asymmetry, the vibrational amplitude
is governed by a perturbed nonlinear Schr?dinger equation instead of the standard one found in one-dimensional lattices with
two alternating masses but uniform force constant. Although the stationary localized modes with carrier wavevector at the
Brillouin-zone boundary are similar to those of ionic lattices, the moving localized modes with wavevectors within the zone
are different owing to the perturbation. The calculation shows that the height of the moving localized modes in this lattice
dampens with time.
Received 14 May 2001 and Received in final form 12 July 2001 相似文献
3.
M. Johansson A.M. Morgante S. Aubry G. Kopidakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):279-283
Modulational instability of travelling plane waves is often considered as the first step in the formation of intrinsically
localized modes (discrete breathers) in anharmonic lattices. Here, we consider an alternative mechanism for breather formation,
originating in oscillatory instabilities of spatially periodic or quasiperiodic nonlinear standing waves (SWs). These SWs
are constructed for Klein-Gordon or Discrete Nonlinear Schr?dinger lattices as exact time periodic and time reversible multibreather
solutions from the limit of uncoupled oscillators, and merge into harmonic SWs in the small-amplitude limit. Approaching the
linear limit, all SWs with nontrivial wave vectors (0 < Q < π) become unstable through oscillatory instabilities, persisting for arbitrarily small amplitudes in infinite lattices.
The dynamics resulting from these instabilities is found to be qualitatively different for wave vectors smaller than or larger
than π/2, respectively. In one regime persisting breathers are found, while in the other regime the system thermalizes.
Received 6 October 2001 / Received in final form 1st March 2002 Published online 2 October 2002
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ID="a"e-mail: mjn@ifm.liu.se 相似文献
4.
M.T. Primatarowa K.T. Stoychev R.S. Kamburova 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):291-294
We investigate the propagation and interaction of solitons associated with circularly polarized vibrations in gyrotropic media.
The chirality of the structure yields different dispersion laws and hence different phase and group velocities for the left-
and right-handed modes. The helical arrangement of the monomers is modelled through first- and third-neighbour interactions.
The dynamics of the excitations is governed by a system of coupled discrete nonlinear Schr?dinger equations which is studied
both analytically and numerically. Depending on the initial conditions and the interaction constants, different evolutionary
patterns are obtained corresponding to unbound or bound one- and two-soliton solutions. The results can be applied to the
process of energy transfer in helical polymers.
Received 1st October 2001 / Received in final form 30 April 2002 Published online 2 October 2002
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ID="a"e-mail: krad@issp.bas.bg 相似文献
5.
J. Lages D.L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(1):129-133
We study analytically and numerically the problem of two particles with a long range attractive interaction on a two-dimensional
(2d) lattice with disorder. It is shown that below some critical disorder the interaction creates delocalized coupled states
near the Fermi level. These states appear inside well localized noninteracting phase and have a form of two-particle ring
which diffusively propagates over the lattice.
Received 29 September 2000 and Received in final form 15 January 2001 相似文献
6.
Michael Öster 《Physica D: Nonlinear Phenomena》2009,238(1):88-99
A two-dimensional nonlinear Schrödinger lattice with nonlinear coupling, modelling a square array of weakly coupled linear optical waveguides embedded in a nonlinear Kerr material, is studied. We find that despite a vanishing energy difference (Peierls-Nabarro barrier) of fundamental stationary modes the mobility of localized excitations is very poor. This is attributed to a large separation in parameter space of the bifurcation points of the involved stationary modes. At these points the stability of the fundamental modes is changed and an asymmetric intermediate solution appears that connects the points. The control of the power flow across the array when excited with plane waves is also addressed and shown to exhibit great flexibility that may lead to applications for power-coupling devices. In certain parameter regimes, the direction of a stable propagating plane-wave current is shown to be continuously tunable by amplitude variation (with fixed phase gradient). More exotic effects of the nonlinear coupling terms like compact discrete breathers and vortices, and stationary complex modes with nontrivial phase relations are also briefly discussed. Regimes of dynamical linear stability are found for all these types of solutions. 相似文献
7.
J. Szeftel G. Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):329-334
The properties of vibrational localized (breathers) and traveling (anharmonic phonons) waves are discussed in an infinite,
one-dimensional, monoatomic crystal for the Fermi-Pasta-Ulam and Frenkel-Kontorova models. The shooting and finite difference
schemes have been implemented to reckon the displacement fields of breathers and anharmonic phonons, respectively. These tools
provide localized and traveling waves proving to be indefinitely stable in simulations carried out by solving the equations
of motion. The emphasis is laid on the role of the cubic and quartic terms of the anharmonic potential which turn out to oppose
and to shore up the restoring force, respectively. The case of vibrational modes arising in an anharmonic crystal subject
to a soft phonon induced instability is also addressed.
Received 7 November 2001 and Received in final form 5 February 2002 Published online 6 June 2002 相似文献
8.
We present a comparison of quantum and “semiclassical” trajectories of coherent states that correspond to classical breather solutions of finite discrete nonlinear Schrödinger (DNLS) lattices. The main goal is to explain earlier numerical observations of recurrent return to the vicinity of initial coherent states corresponding to stable breathers that are also spatially localized. This effect can be considered as a quantum manifestation of classical spatial localization. We show that these phenomena are encoded in a simple expression for the distance between the quantum and semiclassical states that involves the basic frequencies of the classical and quantum systems, as well as the breather amplitude and quantum spectral decomposition of the system. A corollary is that recurrence phenomena are robust under perturbation of the initial conditions for stable breathers. 相似文献
9.
M. Holthaus S. Stenholm 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):451-467
We discuss the dynamics of two weakly coupled Bose-Einstein condensates in a double-well potential, contrasting the mean-field
picture to the exact N-particle evolution. On the mean-field level, a self-trapping transition occurs when the scaled interaction strength exceeds
a critical value; this transition essentially persists in small condensates comprising about 1000 atoms. When the double-well
is modulated periodically in time, Floquet-type solutions to the nonlinear Schr?dinger equation take over the role of the
stationary mean-field states. These nonlinear Floquet states can be classified as “unbalanced” or “balanced”, depending on
whether or not they entail long-time confinement of most particles to one well. Since the emergence of unbalanced Floquet
states depends on the amplitude and frequency of the modulating force, we predict that the onset of self-trapping can efficiently
be controlled by varying these parameters. This prediction is verified numerically by both mean-field and N-particle calculations.
Received 5 November 2000 and Received in final form 16 February 2001 相似文献
10.
K.Ø. Rasmussen S. Aubry A.R. Bishop G.P. Tsironis 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):169-175
We study the dynamics of the discrete nonlinear Schr?dinger lattice initialized such that a very long transitory period of
time in which standard Boltzmann statistics is insufficient is reached. Our study of the nonlinear system locked in this non-Gibbsian state focuses on the dynamics of discrete breathers (also called intrinsic localized modes). It is found that part of the
energy spontaneously condenses into several discrete breathers. Although these discrete breathers are extremely long lived,
their total number is found to decrease as the evolution progresses. Even though the total number of discrete breathers decreases
we report the surprising observation that the energy content in the discrete breather population increases. We interpret these
observations in the perspective of discrete breather creation and annihilation and find that the death of a discrete breather
cause effective energy transfer to a spatially nearby discrete breather. It is found that the concepts of a multi-frequency
discrete breather and of internal modes is crucial for this process. Finally, we find that the existence of a discrete breather
tends to soften the lattice in its immediate neighborhood, resulting in high amplitude thermal fluctuation close to an existing
discrete breather. This in turn nucleates discrete breather creation close to a already existing discrete breather.
Received 21 January 1999 and Received in final form 20 September 1999 相似文献
11.
F. Selva J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):441-449
We study the difference between on site Hubbard and long range Coulomb repulsions for two interacting particles in a disordered
chain. The system size L (in units of the lattice spacing) is of the order of the one particle localization length and the energies are taken near
the band center. In the two cases, the limits of weak and strong interactions are characterized by uncorrelated energy levels
and are separated by a crossover regime where the states are more extended and the spectra more rigid. U denoting the interaction strength and t the kinetic energy scale, the crossovers take place for interaction energy to kinetic energy ratios U/t and U/(2tL) of order one, for Hubbard and Coulomb repulsions respectively. While Hubbard repulsion can only yield weak critical chaos
with intermediate spectral statistics, Coulomb repulsion can drive the two particle system to quantum chaos with Wigner-Dyson
spectral statistics. The interaction matrix elements are studied to explain this difference.
Received 21 March 2000 and Received in final form 5 February 2001 相似文献
12.
Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice 下载免费PDF全文
We study the existence and stability of two-dimensional discrete breathers in a two-dimensionai discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling. Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive) and the center of the two-dimensional gap breathers (on a light or a heavy atom). 相似文献
13.
We investigate the stability and phase transition of localized modes in Bose–Einstein Condensates (BECs) in an optical lattice with the discrete nonlinear Schrödinger model by considering both two- and three-body interactions. We find that there are three types of localized modes, bright discrete breather (DB), discrete kink (DK), and multi-breather (MUB). Moreover, both two- and three-body on-site repulsive interactions can stabilize DB, while on-site attractive three-body interactions destabilize it. There is a critical value for the three-body interaction with which both DK and MUB become the most stable ones. We give analytically the energy thresholds for the destabilization of localized states and find that they are unstable (stable) when the total energy of the system is higher (lower) than the thresholds. The stability and dynamics characters of DB and MUB are general for extended lattice systems. Our result is useful for the blocking, filtering, and transfer of the norm in nonlinear lattices for BECs with both two- and three-body interactions. 相似文献
14.
For solitary waves on a monoatomic chain with nearest neighbor interactions the continuum approximation has a limited validity range and exhibits certein mathematical problems. For pulse solitons these problems are overcome by the Quasicontinuum Approach (QCA), and the validity range is considerably extended. We generalize the QCA to oscillatory excitations and derive analytic expressions for bright and dark envelope solitons, limiting ourselves to a polynomial interaction potential with harmonic, cubic and quartic terms. Moreover we describe and apply a numerical iteration procedure in Fourier space in order to take into account discreteness effects in a systematic way. This procedure yields envelope solitons with a width in the order of the lattice constant. In the case of zero velocity these solutions can be compared with intrinsic localized modes derived by other authors. The stability and accuracy of all our solutions are tested by numerical simulations. 相似文献
15.
G.H. Zhou Q.L. Xia J.R. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):207-213
Moving nonlinear localized vibrational modes (i.e. discrete breathers) for the one-dimensional homogenous lattice with quartic anharmonicity are obtained analytically by means
of a semidiscrete approximation plus an integration. In addition to the pulse-envelope type of moving modes which have been
found previously both analytically and numerically, we find that a kink-envelope type of moving mode which has not been reported
before can also exist for such a lattice system. The two types of modes in both right- and left-moving form can occur with
different carrier wavevectors and frequencies in separate parts of the plane. Numerical simulations are performed and their results are in good agreement with the analytical predictions.
Received 13 October 1999 and Received in final form 15 May 2000 相似文献
16.
P.G. Kevrekidis B.A. Malomed Z. Musslimani 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):421-436
A model including two nonlinear chains with linear and nonlinear couplings between them, and opposite signs of the discrete
diffraction inside the chains, is introduced. In the case of the cubic [ χ(3)] nonlinearity, the model finds two different interpretations in terms of optical waveguide arrays, based on the diffraction-management
concept. A continuum limit of the model is tantamount to a dual-core nonlinear optical fiber with opposite signs of dispersions
in the two cores. Simultaneously, the system is equivalent to a formal discretization of the standard model of nonlinear optical
fibers equipped with the Bragg grating. A straightforward discrete second-harmonic-generation [ χ(2)] model, with opposite signs of the diffraction at the fundamental and second harmonics, is introduced too. Starting from
the anti-continuum (AC) limit, soliton solutions in the χ(3) model are found, both above the phonon band and inside the gap. Solitons above the gap may be stable as long as they exist,
but in the transition to the continuum limit they inevitably disappear. On the contrary, solitons inside the gap persist all
the way up to the continuum limit. In the zero-mismatch case, they lose their stability long before reaching the continuum
limit, but finite mismatch can have a stabilizing effect on them. A special procedure is developed to find discrete counterparts
of the Bragg-grating gap solitons. It is concluded that they exist at all the values of the coupling constant, but are stable
only in the AC and continuum limits. Solitons are also found in the χ(2) model. They start as stable solutions, but then lose their stability. Direct numerical simulations in the cases of instability
reveal a variety of scenarios, including spontaneous transformation of the solitons into breather-like states, destruction
of one of the components (in favor of the other), and symmetry-breaking effects. Quasi-periodic, as well as more complex,
time dependences of the soliton amplitudes are also observed as a result of the instability development.
Received 14 September 2002 / Received in final form 4 February 2003 Published online 24 April 2003
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ID="a"e-mail: malomed@eng.tau.ac.il 相似文献
17.
K. Kundu B.C. Gupta 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):23-33
We study the formation of stationary localized states using the discrete nonlinear Schr?dinger equation in a Cayley tree with
connectivity K. Two cases, namely, a dimeric power law nonlinear impurity and a fully nonlinear system are considered. We introduce a transformation
which reduces the Cayley tree into an one dimensional chain with a bond defect. The hopping matrix element between the impurity
sites is reduced by . The transformed system is also shown to yield tight binding Green's function of the Cayley tree. The dimeric ansatz is used
to find the reduced Hamiltonian of the system. Stationary localized states are found from the fixed point equations of the
Hamiltonian of the reduced dynamical system. We discuss the existence of different kinds of localized states. We have also
analyzed the formation of localized states in one dimensional system with a bond defect and nonlinearity which does not correspond
to a Cayley tree. Stability of the states is discussed and stability diagram is presented for few cases. In all cases the
total phase diagram for localized states have been presented.
Received: 18 September 1997 / Revised: 31 October and 17 november 1997 / Accepted: 19 November 1997 相似文献
18.
D. Weinmann P. Schmitteckert R.A. Jalabert J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):139-156
We study the delocalization effect of a short-range repulsive interaction on the ground state of a finite density of spinless
fermions in strongly disordered one dimensional lattices. The density matrix renormalization group method is used to explore
the charge density and the sensitivity of the ground state energy with respect to the boundary condition (the persistent current)
for a wide range of parameters (carrier density, interaction and disorder). Analytical approaches are developed and allow
to understand some mechanisms and limiting conditions. For weak interaction strength, one has a Fermi glass of Anderson localized
states, while in the opposite limit of strong interaction, one has a correlated array of charges (Mott insulator). In the
two cases, the system is strongly insulating and the ground state energy is essentially invariant under a twist of the boundary
conditions. Reducing the interaction strength from large to intermediate values, the quantum melting of the solid array gives
rise to a more homogeneous distribution of charges, and the ground state energy changes when the boundary conditions are twisted.
In individual chains, this melting occurs by abrupt steps located at sample-dependent values of the interaction where an (avoided)
level crossing between the ground state and the first excitation can be observed. Important charge reorganizations take place
at the avoided crossings and the persistent currents are strongly enhanced around the corresponding interaction value. These
large delocalization effects become smeared and reduced after ensemble averaging. They mainly characterize half filling and
strong disorder, but they persist away of this optimal condition.
Received 5 July 2000 and Received in final form 8 November 2000 相似文献
19.
The system consisting of a chain of parametrically driven and damped nonlinear coupled pendula with a mass impurity is studied by means of a discrete version of the envelope function approach. An analogue of the parametrically driven damped nonlinear Schodinger equation with an impurity term is derived from the original lattice equation. Analytical solutions of impurity pinned high-frequency breathers and kinks are obtained. The results show that the mass impurity has striking influence on the high-frequency modes. In addition, we perform numerical simulations, showing that the light mass impurity has a stabilizing effect on the chain. The breathers seeding chaos in the homogeneous chain are pinned on a suitable light impurity to pull the chain from the chaotic state. 相似文献
20.
S. Fratini P. Quémerais 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):41-49
We consider a three dimensional Wigner crystal of electrons lying in a host ionic dielectric. Owing to their interaction with
the lattice polarization, each localized electron forms a polaron. We study the collective excitations of such a polaronic
Wigner crystal at zero temperature, taking into account the quantum fluctuations of the polarization within the Feynman harmonic
approximation. We show that, contrary to the ordinary electron crystal, the system undergoes a polarization catastrophe when
the density is increased. An optical signature of this instability is derived, whose trend agrees with the experiments carried
out in Nd-based cuprates.
Received 4 July 2002 Published online 17 September 2002 相似文献