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arXiv 1604.08809cond-mat.quant-gas
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用多组态含时Hartree方法研究Hubbard哈密顿量的动力学

Dynamics of Hubbard Hamiltonians with the multiconfigurational time-dependent Hartree method for indistinguishable particles

Axel U. J. Lode, Christoph Bruder

摘要:

我们适用于不可区分粒子的多组态含时Hartree方法(MCTDH-X)的哈伯德型哈密顿描述的长程或短程粒子间相互作用的晶格中的玻色子或费米子系统。波函数扩展在变分优化的时间相关的多体基础上产生的一组有效的创建运营商,相关的原始粒子创建运营商的时间相关的酉变换。我们使用含时变分原理的系数,这种变换以及在含时多体基础的波函数的展开系数作为变分参数导出的运动方程。MCTDH-X的收敛性通过将其结果与具有接触相互作用的玻色子填充的一维、二维和三维晶格的精确对角化进行比较来示出。我们使用MCTDH-X来研究加载到一个大的二维晶格中的玻色-爱因斯坦凝聚体的长时间分裂动力学中的相关性的建立,该晶格受到在中心倾斜的势垒的影响。我们发现,该系统被分成两个部分与紧急的时间依赖性的相关性,取决于斜坡的时间-对于大多数障碍提高时间的系统成为两重碎片,但对于一些非常快的斜坡,该系统显示复苏的连贯性。

英文摘要:

We apply the multiconfigurational time-dependent Hartree method for indistinguishable particles (MCTDH-X) to systems of bosons or fermions in lattices described by Hubbard type Hamiltonians with long-range or short-range interparticle interactions. The wavefunction is expanded in a variationally optimized time-dependent many-body basis generated by a set of effective creation operators that are related to the original particle creation operators by a time-dependent unitary transform. We use the time-dependent variational principle for the coefficients of this transform as well as the expansion coefficients of the wavefunction in the time-dependent many-body basis as variational parameters to derive equations of motion. The convergence of MCTDH-X is shown by comparing its results to the exact diagonalization of one-, two-, and three-dimensional lattices filled with bosons with contact interactions. We use MCTDH-X to study the buildup of correlations in the long-time splitting dynamics of a Bose-Einstein condensate loaded into a large two-dimensional lattice subject to a barrier that is ramped up in the center. We find that the system is split into two parts with emergent time-dependent correlations that depend on the ramping time -- for most barrier-raising-times the system becomes two-fold fragmented, but for some of the very fast ramps, the system shows revivals of coherence.

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