arXiv 1104.43502011-04-21cond-mat.quant-gas

振动二维正方形光晶格中的量子动量玻色-爱因斯坦凝聚体

Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices

M. Di Liberto, O. Tieleman, V. Branchina, C. Morais Smith

备注：: 7 pages, 7 figures
发表信息：: Phys. Rev. A 84, 013607 (2011)
DOI：: 10.1103/PhysRevA.84.013607

摘要：

我们考虑了二维正方形光晶格中的超冷玻色子，用玻色-哈伯德模型描述。此外，一个外部的时间相关的正弦力施加到系统，沿着对角线之一的晶格振动。振动的效果是重新归一化的最近邻跳变系数，可以任意减少，可以消失，甚至可以改变符号，这取决于振动参数。因此，有必要考虑高阶跳跃项，这是不同的重整化的震动，并引入各向异性的问题。我们表明，这些不同的跳跃项之间的竞争导致有限动量凝聚，与动量，可以通过调整的震动的强度。我们计算了莫特绝缘体和不同的超流相之间的边界，并提出了飞行时间的图像，预计将在实验中观察到。我们的研究结果开辟了新的可能性，实现玻色子类似物的FFLO相描述非均匀超导性。

英文摘要：

We consider ultracold bosons in a 2D square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. It is therefore necessary to account for higher-order hopping terms, which are renormalized differently by the shaking, and introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates, with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott-insulator and the different superfluid phases, and present the time-of-flight images expected to be observed experimentally. Our results open up new possibilities for the realization of bosonic analogs of the FFLO phase describing inhomogeneous superconductivity.

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