论文标题
二维Bose-Hubbard Lattices的膨胀动力学：Bose-Einstein冷凝物和热云
Expansion dynamics in two-dimensional Bose-Hubbard lattices: Bose-Einstein condensate and thermal cloud
论文作者
论文摘要
我们研究了二维平方光学晶格中超电压胶气的时间膨胀。气体是由玻色 - 哈伯德模型在超级流体政策深处描述的，最初所有玻色子都凝结在晶格的中央位置。我们使用先前开发的非平衡传播方法来捕获相互作用的玻体系统的时间演变，其中多体汉密尔顿人在适当的局部基础上表示，并将相应的现场运算符分离为经典的[Bose-Inerstein Condensectate（BEC）]部分和量子机械波动。淬火后，即在晶格突然切换最近的邻居跳动后，膨胀的，玻色云将空间分离为快速，弹道的先驱，并缓慢扩展由自我捕捞控制的中心部分。我们表明，先驱者的扩展是由BEC的一致动力学驱动的，并且其速度与Lieb-Robinson界限一致。对于较小的晶格，我们分析了准粒子碰撞如何导致凝结物耗尽和振荡阻尼的增强。
We study the temporal expansion of an ultracold Bose gas in two-dimensional, square optical lattices. The gas is described by the Bose-Hubbard model deep in the superfluid regime, with initially all bosons condensed in the central site of the lattice. We use the previously developed nonequilibrium propagator method for capturing the time evolution of an interacting bosonic system, where the many-body Hamiltonian is represented in an appropriate local basis and the corresponding field operators are separated into the classical [Bose-Einstein condensate (BEC)] part and quantum mechanical fluctuations. After a quench, i.e. after a sudden switch of the lattice nearest-neighbor hopping, the expanding, bosonic cloud separates spatially into a fast, ballistic forerunner and a slowly expanding central part controlled by selftrapping. We show that the forerunner expansion is driven by the coherent dynamics of the BEC and that its velocity is consistent with the Lieb-Robinson bound. For smaller lattices we analyze how quasiparticle collisions lead to enhanced condensate depletion and oscillation damping.
