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arXiv 1002.1393nlin.PS
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椭圆晶格势中的二维带隙孤子

Two-dimensional gap solitons in elliptic-lattice potentials

Yingji He, Boris A. Malomed, Bambi Hu

摘要:

在具有自吸引或自排斥的Gross-Pitaevskii方程(GPE)框架下,研究了椭圆变形的同心晶格势场中的二维物质波带隙孤子.对于一个固定的偏心率的晶格,孤子家庭中发现的排斥和吸引的模型。在前一种情况下,分析表明,在第一个椭圆形槽(最靠近中心的环形势极小值)中捕获了两种间隙孤子:椭圆环形孤子(EAS)和双孤子(DS),双孤子是由两个紧密局域的密度峰形成的,它们之间的相位差为零。随着范数的减小,EAS中沿方位角方向的密度分布从近似均匀变为双峰,并最终变为DS。在吸引模型中,在椭圆槽中只存在DS,而没有发现EAS,所有没有角动量(l = 0)的孤子都是完全稳定的。对于l不等于0,涡旋孤子-具有足够大的范数的EAS(在排斥模型中)和DS(在具有两个非线性符号的模型中)-是准稳定的,在椭圆槽中表现出摇摆运动(我们考虑l=1和l=2的情况)。在较小的范数值下,涡旋环形孤子(在排斥模型中)是不稳定的。利用变分近似和数值方法,研究了在吸引和排斥两种模型下,中心势阱中稳定的基本孤子。

英文摘要:

We study two-dimensional (2D) matter-wave gap solitons trapped in an elliptically deformed concentric lattice potential, within the framework of the Gross-Pitaevskii equation (GPE) with self-attraction or self-repulsion. For a fixed eccentricity of the lattice, soliton families are found in both the repulsive and attractive models. In the former case, the analysis reveals two kinds of gap solitons trapped in the first oval trough (the ring-shaped potential minimum closest to the center): elliptic annular solitons (EASs), and double solitons (DSs), which are formed by two tightly localized density peaks located at diametrically opposite points of the trough, with zero phase difference between them. With the decrease of the norm, the density distribution in the EAS along the azimuthal direction changes from nearly-uniform to double-peaked and, eventually, to the DS. In the attractive model, there exist only DSs in the oval trough, while EASs are not found. All such solitons without the angular momentum (l = 0) are fully stable. For l is not equal to 0, vortical solitons - both EASs with a sufficiently large norm (in the repulsive model) and DSs (in models with both signs of the nonlinearity) - are quasi-stable, exhibiting rocking motion in the elliptic trough (we consider the cases of l=1 and l=2). At smaller values of the norm, the vortical annular solitons (in the repulsive model) are unstable. Stable fundamental solitons trapped in the central potential well are investigated too, in both the attractive and repulsive models, by means of the variational approximation and numerical methods.

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