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Ennio Arimondo 《量子光学学报》2006,12(B08):59-60
Cold atoms and, more recently, Bose-Einstein condensates (BEC's) in optical lattices have attracted increasing interest since their first realization. In particular, the formal similarity between the wavefunction of a BEC inside the periodic potential of an optical lattice and of the electrons in a crystal lattice has triggered theoretical and experimental efforts alike. Many phenomena from condensed matter physics, such as Bloch oscillations and Landau-Zener tunneling have been shown to be observable also in optical lattices. An important difference between electrons in a crystal lattice and a BEC inside the periodic potential of an optical lattice is the strength of the self interaction and hence the magnitude of the nonlinearity of the system. Electrons in a metal are almost noninteracting, whereas atoms inside a BEC interact strongly. A' perturbation approach is appropriate in the former case while in the latter the full nonlinearity must be taken into account. From this feature new physics is expected. Most experiments to date have been carried out in the regime of shallow lattice depth, for which the system is well described by the mean field Gross-Pitaevskii equation with a periodic potential. Moreover, the nonlinearity induced by the mean-field of the condensate has been shown, both theoretically and experimentally, to give rise to instabilities in certain regions of the Brillouin zone. These instabilities are not present in the corresponding linear system, i.e. the electron system. Experimental and theoretical results on the subject of nonlinear Landau-Zener tunneling and nonlinearity-induced instabilities in a Bose-Einstein condensate interacting with an external periodic potential will be presented. 相似文献
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Effects of External Electric Field on Ferroelectric Superlattice with Two Alternating Layers 下载免费PDF全文
The effects of the external electric field on the ferroelectric superlattice with two alternating layers have been studied using the transverse Ising model based on the effective-field theory with the differential technique. The hysteresis loops and susceptibility of the system have been given. The stronger the external electric field, the smaller the susceptibility, reflecting that the polarization is weaker. 相似文献
4.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
5.
We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18,20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100 nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w^- to the average crystal size D^- for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D^-, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12 kOe of the ribbons versus x. 相似文献
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离子晶体非简谐振动引起的光学非线性与增强吸收型光双稳 总被引:3,自引:2,他引:1
处理了光场与离子晶体的非简谐性振动之间的相互作用问题。导出了用简正坐标即声子模式所表达的非线性晶格动力学和非线性宏观极化。在旋转波近似下,得到在入射光驱动下光子-声子耦合体系的总的相干性哈密顿算符。 相似文献
7.
李映明 《理化检验(化学分册)》1995,31(6):359-360
钢铁热浸镀锌量的测定在GB及世界各国标准里均采用三氯化锑法。因其产生SbH_3有毒气体而被甲醛或乌洛托品代替锑剂。ZBH11001-88采用甲醛,GB/T13825-92及ISO1460-1992(E)均采用乌洛托品。本文对乌洛托品方法进行试验并与三氯化锑法、ZBH11001-88法加以研究比较。 1 试验部分 1.1 主要试剂 乌洛托品(六次甲基四胺,分析纯,含甲醛97%以上) 乌洛托品盐酸退镀溶液,称取乌洛托品3.5g溶于盐酸(1+1)1L中。 1.2 测定步骤 将热浸镀锌钢铁试样制备成可测面积的样品,以无水乙醇及乙醚清除表面油污,烘干冷至室温于万分之一天平上称准至毫克。置于盛有乌洛托品退镀溶液的器皿中,保持样品每平方厘米表面上有10ml以上的 相似文献
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Exact Solution of an Extended Hubbard Model with Electron—Lattice Interaction for an Organic Ferromagnetic Polymer 下载免费PDF全文
Using an exact diagonalization method,we study an extended Hubbard model with an electron-lattice interaction for an organic ferromagnetic chain with radical coupling.The result shows that the ferromagnetic ground state originates from the antiferromagnetic correlation between adjoining sites,which is enhanced by the on-site e-e repulsion.The intersite e-e repulsion induces the inhomogeneous distribution of the charge density.The dimerization is decreased by the e-e interaction and the radical coupling.The electron-lattice interaction and the radical coupling can transfer the spin density and charge density between the main chain and the radicals. 相似文献
10.
利用对德拜模式密度的修正入手,重新讨论了频率函数的热容量,得到了在高、低温极限与实验相符合的结论,该模型保留了德拜模型的优点,又对其不足之外进行了修正,同时给出了修正项的来源。 相似文献