共查询到20条相似文献,搜索用时 15 毫秒
1.
Solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
By use of the Hartree approximation and the method of multiple scales, we
investigate quantum solitons and intrinsic localized modes in a
one-dimensional antiferromagnetic chain. It is shown that there exist
solitons of two different quantum frequency bands: i.e., magnetic optical
solitons and acoustic solitons. At the boundary of the Brillouin zone, these
solitons become quantum intrinsic localized modes: their quantum
eigenfrequencies are below the bottom of the harmonic optical frequency band
and above the top of the harmonic acoustic frequency band. 相似文献
2.
具有格点各向异性的一维铁磁链中的量子孤子和内禀局域模(英文) 总被引:1,自引:0,他引:1
基于Hartree-Fock方法和多标度方法,我们考察了具有格点各向异性的一维铁磁链中的量子孤子和内禀局域模,量子磁振子的波函数由量子包络孤子来描述.在布里渊区边界,量子包络孤子变成了量子内禀局域模,它的量子本征频率在简谐波带的顶部上方,量子磁振子主要集中在中心位置j=j0的附近. 相似文献
3.
在一维均匀铁磁链中磁振动的内禀局域模 总被引:2,自引:2,他引:0
利用多标度方法和准离散近似,我们考察了在一维均匀铁磁链中磁振动的内禀局域模; 结果表明磁振动的内禀局域模在许多方面都与晶格振动的内禀局域模相类似;它们是近邻自旋之间非线性相互作用的结果.这种内禀局域模的存在并没有破坏系统的平移对称性,它们能在任何晶格位被激发.它们的量子本征频率在简谐磁振动频带的上方. 相似文献
4.
M. Stojanovi?A. Maluckov Lj. Had?ievskiB.A. Malomed 《Physica D: Nonlinear Phenomena》2011,240(18):1489-1496
Fundamental solitons pinned to the interface between three semi-infinite one-dimensional nonlinear dynamical chains, coupled at a single site, are investigated. The light propagation in the respective system with the self-attractive on-site cubic nonlinearity, which can be implemented as an array of nonlinear optical waveguides, is modeled by the system of three discrete nonlinear Schrödinger equations. The formation, stability and dynamics of symmetric and asymmetric fundamental solitons centered at the interface are investigated analytically by means of the variational approximation (VA) and in a numerical form. The VA predicts that two asymmetric and two antisymmetric branches exist in the entire parameter space, while four asymmetric modes and the symmetric one can be found below some critical value of the inter-lattice coupling parameter—actually, past the symmetry-breaking bifurcation. At this bifurcation point, the symmetric branch is destabilized and two new asymmetric soliton branches appear, one stable and the other unstable. In this area, the antisymmetric branch changes its character, getting stabilized against oscillatory perturbations. In direct simulations, unstable symmetric modes radiate a part of their power, staying trapped around the interface. Highly unstable asymmetric modes transform into localized breathers traveling from the interface region across the lattice without significant power loss. 相似文献
5.
By using a full quantum approach based on the time-dependent Hartree approximation and the semidiscrete multiple-scale method, we study quantum nonlinear excitations in a one-dimensional ferromagnetic chain with octupole-dipole interaction and on-site uniaxial anisotropy. We find that quantum solitons and breathers can exist in the ferromagnetic chain, and analyze existence conditions of these excitations. Since the system states corresponding to quantum breathers are stationary states, we can get the energy level formula of such quantum breathers. 相似文献
6.
We reveal the existence of asymmetric vortex solitons in ideally symmetric periodic lattices and show how such nonlinear localized structures describing elementary circular flows can be analyzed systematically using the energy-balance relations. We present the examples of rhomboid, rectangular, and triangular vortex solitons on a square lattice and also describe novel coherent states where the populations of clockwise and anticlockwise vortex modes change periodically due to a nonlinearity-induced momentum exchange through the lattice. Asymmetric vortex solitons are expected to exist in different nonlinear lattice systems, including optically induced photonic lattices, nonlinear photonic crystals, and Bose-Einstein condensates in optical lattices. 相似文献
7.
Bright and dark small amplitude nonlinear localized modes in a quantum one-dimensional Klein--Gordon chain 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
By means of the Glauber's coherent state method combined with multiple-scale method, this paper investigates the localized modes in a quantum one-dimensional Klein-Gordon chain and finds that the equation of motion of annihilation operator is reduced to the nonlinear Schroedinger equation. Interestingly, the model can support both bright and dark small amplitude travelling and non-travelling nonlinear localized modes in different parameter spaces. 相似文献
8.
We discover that, at the edge of an optical lattice imprinted in a saturable nonlinear medium, one-dimensional surface solitons exist only within a band of light intensities and that they cease to exist when the lattice depth exceeds an upper threshold. We also reveal the generation of arrays of two-dimensional surface solitons mediated by the transverse modulational instability of one-dimensional solitons, a process that is found to exhibit specific features associated to properties of the optical lattice. 相似文献
9.
The quantum solitary wave solutions in
a one-dimensional ferromagnetic chain is investigated by using the
Hartree-Fock approach and the multiple-scale method. It is shown
that quantum solitary wave solutions can exist in a ferromagnetic
system with nearest- and next-nearest-neighbor exchange
interaction, and at the certain value of the first Brillouin zone,
the solitary wave solution of the Hartree wave function becomes the
intrinsic localized mode. 相似文献
10.
Dynamical properties of discrete solitons in nonlinear Schr?dinger lattices with saturable nonlinearity are studied in the framework of the one-dimensional discrete Vinetskii-Kukhtarev model. Two stationary strongly localized modes, centered on site (A) and between two neighboring sites (B), are obtained. The associated Peierls-Nabarro potential is bounded and has multiple zeros indicating strong implications on the stability and dynamics of the localized modes. Besides a stable propagation of mode A, a stable propagation of mode B is also possible. The enhanced ability of the large power solitons to move across the lattice is pointed out and numerically verified. 相似文献
11.
The nonlinear lattice — a new and nonlinear class of periodic potentials — was recently introduced to generate various nonlinear localized modes. Several attempts failed to stabilize two-dimensional (2D) solitons against their intrinsic critical collapse in Kerr media. Here, we provide a possibility for supporting 2D matter-wave solitons and vortices in an extended setting — the cubic and quintic model — by introducing another nonlinear lattice whose period is controllable and can be different from its cubic counterpart, to its quintic nonlinearity, therefore making a fully “nonlinear quasi-crystal”.A variational approximation based on Gaussian ansatz is developed for the fundamental solitons and in particular, their stability exactly follows the inverted Vakhitov–Kolokolov stability criterion, whereas the vortex solitons are only studied by means of numerical methods. Stability regions for two types of localized mode — the fundamental and vortex solitons — are provided. A noteworthy feature of the localized solutions is that the vortex solitons are stable only when the period of the quintic nonlinear lattice is the same as the cubic one or when the quintic nonlinearity is constant, while the stable fundamental solitons can be created under looser conditions. Our physical setting (cubic-quintic model) is in the framework of the Gross–Pitaevskii equation or nonlinear Schrödinger equation, the predicted localized modes thus may be implemented in Bose–Einstein condensates and nonlinear optical media with tunable cubic and quintic nonlinearities. 相似文献
12.
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
13.
We introduce a novel class of stable nonlinear modes trapped in a lower-index film core sandwiched between two optical lattices, or in the cylindrical core of a radial lattice, imprinted in defocusing media. Such a family of nonlinear modes transforms into defect lattice solitons when the core width is sufficiently small or into an array of kinks when the width is large enough. We find that higher-order modes with multiple zeros inside the guiding core can be stable in one-dimensional settings. 相似文献
14.
The steady-state energy distribution of thermal vibrations at a given ambient temperature has been investigated based on a simple mathematical model that takes into account central and noncentral interactions between carbon atoms in a one-dimensional carbyne chain. The investigation has been performed using standard asymptotic methods of nonlinear dynamics in terms of the classical mechanics. In the first-order nonlinear approximation, there have been revealed resonant wave triads that are formed at a typical nonlinearity of the system under phase matching conditions. Each resonant triad consists of one longitudinal and two transverse vibration modes. In the general case, the chain is characterized by a superposition of similar resonant triplets of different spectral scales. It has been found that the energy equipartition of nonlinear stationary waves in the carbyne chain at a given temperature completely obeys the standard Rayleigh–Jeans law due to the proportional amplitude dispersion. The possibility of spontaneous formation of three-frequency envelope solitons in carbyne has been demonstrated. Heat in the form of such solitons can propagate in a chain of carbon atoms without diffusion, like localized waves. 相似文献
15.
The 3D solitons and vortices in 3D discrete monatomic lattices with cubic
and quartic nonlinearity
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
By virtue of the method of multiple-scale and the quasi-discreteness
approach, we have discussed the nonlinear vibration equation of a 3D
discrete monatomic lattice with its nearest-neighbours interaction. The 3D
simple cubic lattices have the same localized modes as a 1D discrete
monatomic chain with cubic and quartic nonlinearity. The nonlinear vibration
in the 3D simple cubic lattice has 3D distorted solitons and 3D envelop
solitons in the direction of $k_{x}=k_{y}=k_{z}=k$ and $k=\pm
\pi$/6$a_{0}$ in the
Brillouin zone, as well as has 3D vortices in the direction of
$k_{x}=k_{y}=k_{z}=k$ and $k=\pm \pi$/$a_{0}$ in the Brillouin zone. 相似文献
16.
Manuel G. Velarde Alexander P. Chetverikov Werner Ebeling Sergey V. Dmitriev Victor D. Lakhno 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(10):233
The excitation of solitons and discrete breathers (pinned or otherwise, also known asintrinsic localized modes, DB/ILM) in a one-dimensional lattice, also denoted as a chain,is considered when both on-site and inter-site vibrations, coupled together, are governedby the empirical Morse interaction. We focus attention on the transformation of the formerinto the latter as the relative strength of the on-site potential to that of theinter-site potential is increased. 相似文献
17.
We study surface modes at the edge of a semi-infinite chirped photonic lattice in the framework of an effective discrete nonlinear model. We demonstrate that the lattice chirp can change dramatically the conditions for the mode localization near the surface, and we find numerically the families of discrete surface solitons in this case. Such solitons do not require any minimum power to exist provided the chirp parameter exceeds some critical value. We also analyze how the chirp modifies the interaction of a soliton with the lattice edge. 相似文献
18.
囚禁在光学晶格中的旋量凝聚体由于其长的相干性和可调控性,使其成为时下热点的多比特量子计算的潜在候选载体,清楚地了解该体系的自旋和磁性的产生和调控就显得尤为重要.本文主要从理论上回顾了光晶格原子自旋链的磁性的由来和操控手段.从激光冷却原子出发,制备旋量玻色-爱因斯坦凝聚体,并装载进光晶格,最后实现原子自旋链,对整个过程的理论研究进行了综述;就如何产生和操控自旋激发进行了详细探讨,其中包括磁孤子的制备;讨论了如何将原子自旋链应用于量子模拟.对光学晶格中的磁激发研究将会对其在冷原子物理、凝聚态物理、量子信息等各方向的应用起指导性作用. 相似文献
19.
We show that the balance between localized gain and nonlinear cubic dissipation in the two-dimensional nonlinear Schr?dinger equation allows for the existence of stable localized modes that we identify as solitons. Such modes exist only when the gain is strong enough and the energy flow exceeds certain threshold value. Above the critical value of the gain, symmetry breaking occurs and asymmetric dissipative solitons emerge. 相似文献
20.
The formation of unstaggered localized modes in dynamical lattices can be supported by the interplay of discreteness and nonlinearity with a finite relaxation time. In rapidly responding nonlinear media, on-site discrete solitons are stable, and their broad intersite counterparts are marginally stable, featuring a virtually vanishing real instability eigenvalue. The solitons become unstable in the case of the slowly relaxing nonlinearity. The character of the instability alters with the increase of the delay time, which leads to a change in the dynamics of unstable discrete solitons. They form robust localized breathers in rapidly relaxing media, and decay into oscillatory diffractive pattern in the lattices with a slow nonlinear response. Marginally stable solitons can freely move across the lattice. 相似文献