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arXiv 1101.2666cond-mat.quant-gas
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光晶格中轻费米原子和重玻色原子预成分子的效率:强耦合展开法

Efficiency for preforming molecules from mixtures of light Fermi and heavy Bose atoms in optical lattices: the strong-coupling-expansion method

Anzi Hu, J. K. Freericks, M. M. Maśka, C. J. Williams

摘要:

讨论了强耦合展开(跳跃中的微扰理论)在研究光晶格中轻费米重玻色(如$^{40}$ K- $^{87}$ Rb)混合物中的应用。我们使用强耦合方法来评估预形成分子的效率,每个粒子的熵和热涨落。我们表明,在强相互作用制度(并在高温下),强耦合膨胀是一种经济的方式来研究这个问题。在某些情况下,它仍然有效,甚至下降到低温。由于计算工作量最小,强耦合方法允许我们使用更大的系统尺寸,可以消除边界效应,这在较高温度下特别重要。由于强耦合方法是如此有效和准确,它允许人们快速扫描参数空间,以优化晶格上分子的预形成(通过选择晶格深度和物种间吸引力)。在强耦合计算的基础上,我们测试了基于涨落耗散定理的测温方案,发现该方案即使在很低的温度下也能给出准确的温度估计。我们相信这种方法和计算结果将有助于下一代实验的设计,并有望导致在量子简并状态下形成偶极物质的能力。

英文摘要:

We discuss the application of a strong-coupling expansion (perturbation theory in the hopping) for studying light-Fermi-heavy-Bose (like $^{40}$K-$^{87}$Rb) mixtures in optical lattices. We use the strong-coupling method to evaluate the efficiency for pre-forming molecules, the entropy per particle and the thermal fluctuations. We show that within the strong interaction regime (and at high temperature), the strong-coupling expansion is an economical way to study this problem. In some cases, it remains valid even down to low temperatures. Because the computational effort is minimal, the strong-coupling approach allows us to work with much larger system sizes, where boundary effects can be eliminated, which is particularly important at higher temperatures. Since the strong-coupling approach is so efficient and accurate, it allows one to rapidly scan through parameter space in order to optimize the pre-forming of molecules on a lattice (by choosing the lattice depth and interspecies attraction). Based on the strong-coupling calculations, we test the thermometry scheme based on the fluctuation-dissipation theorem and find the scheme gives accurate temperature estimation even at very low temperature. We believe this approach and the calculation results will be useful in the design of the next generation of experiments, and will hopefully lead to the ability to form dipolar matter in the quantum degenerate regime.

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