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arXiv 1012.2465nlin.PScond-mat.quant-gas
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非线性晶格中周期和孤立物质波的精确解

Exact solutions for periodic and solitary matter waves in nonlinear lattices

C. H. Tsang, Boris A. Malomed, K. W. Chow

摘要:

我们产生三个巨大的类的精确周期和孤子解的一维Gross-Pitaevskii方程(GPE)的赝势的形式的非线性晶格(NL),诱导的空间周期调制的本地非线性。众所周知,玻色-爱因斯坦凝聚体(BEC)中的非线性激光可以通过Feshbach共振技术产生。该模型还可以包括具有相同周期性的线性势。NL调制函数、线性势(如果有的话)和相应的精确解用三种类型的雅可比椭圆函数cn、dn和sn表示,这三种类型的椭圆函数产生了三种不同的解。在没有线性势的情况下,势和相关的解由两个自由常数和一个附加的符号参数来参数化。在存在后者的情况下,解族具有两个额外的自由参数。这些家族包括符号恒定和符号变化的NL。解的密度极大值可能与周期赝势的极小值或极大值重合。在无限周期的极限下,解化为孤子。通过GPE的直接模拟测试解决方案的稳定性。结果,确定了周期解和孤子的稳定区域。CN型的周期图案,以及相应的极限形式的解决方案,在亮孤子的形式,可能是稳定的,在线性势的存在和不存在。另外两类解的稳定性,dn和sn型,只有在线性势的情况下才可能。

英文摘要:

We produce three vast classes of exact periodic and soliton solutions to the one-dimensional Gross-Pitaevskii equation (GPE) with the pseudopotential in the form of a nonlinear lattice (NL), induced by a spatially periodic modulation of the local nonlinearity. It is well known that NLs in Bose-Einstein condensates (BECs) may be created by means of the Feshbach-resonance technique. The model may also include linear potentials with the same periodicity. The NL modulation function, the linear potential (if any), and the corresponding exact solutions are expressed in terms of the Jacobi's elliptic functions of three types, cn, dn, and sn, which give rise to the three different classes of the solutions. The potentials and associated solutions are parameterized by two free constants and an additional sign parameter in the absence of the linear potential. In the presence of the latter, the solution families feature two additional free parameters. The families include both sign-constant and sign-changing NLs. Density maxima of the solutions may coincide with either minima or maxima of the periodic pseudopotential. The solutions reduce to solitons in the limit of the infinite period. The stability of the solutions is tested via direct simulations of the GPE. As a result, stability regions are identified for the periodic solutions and solitons. The periodic patterns of the cn type, and the respective limit-form solutions in the form of bright solitons, may be stable both in the absence and presence of the linear potential. The stability of the two other solution classes, of the dn and sn types, is only possible with the linear potential.

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