Fast and selective interband transfer of ultracold atoms in bichromatic lattices permitting Dirac points
Fast and selective interband transfer of ultracold atoms in bichromatic lattices permitting Dirac points
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DOI：
10.1103/physreva.99.013621
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发表时间：
2018-06
影响因子：
2.9
通讯作者：
Tomotake Yamakoshi;S. Watanabe
中科院分区：
文献类型：
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作者：
Tomotake Yamakoshi;S. Watanabe
北京的一个实验组[Yueyang Zhai et al.，A 87，063638（2013）]介绍了驻波脉冲序列的方法，用于有效地将超冷玻色子原子制备到一维光学晶格中的特定激发带中。在这里，我们报告了他们的工作对一维双色超晶格问题的理论扩展，以了解更高频段的波包成形过程。改变晶格参数会导致所谓的狄拉克点，一对激发带交叉。因此，本文讨论了同时有效的激发波包附近的狄拉克点及其随后的动力学在力场中的抛物陷阱。我们数值探索最佳的脉冲序列参数，并找到一个优化的序列，激发超过99%的原子在一个理想的情况下的第一和第二激发带内100 $\ensuremath{\mu}\mathrm{s}$。我们的主要发现是，允许狄拉克点的系统具有一个区域的参数，激发能带成为近抛物线，有利于一个强大的波包具有高相干性和等时性。我们还提供了一个适当的数据集，为未来的实验，包括原子-原子相互作用的平均场非线性项的方式的影响。
An experimental group in Beijing [Yueyang Zhai et al., Phys. Rev. A 87, 063638 (2013)] introduced the method of the standing-wave pulse sequence for efficiently preparing ultracold bosonic atoms into a specific excited band in a one-dimensional optical lattice. Here, we report on a theoretical extension of their work to the problem of one-dimensional bichromatic superlattices in order to understand a wave packet shaping process in higher bands. Varying the lattice parameters leads to the so-called Dirac point where a pair of excited bands crosses. This paper thus discusses simultaneously efficient excitation of the wave packet to the proximity of the Dirac point and its subsequent dynamics in the force field of a parabolic trap. We numerically explore optimal pulse-sequence parameters and find an optimized sequence which excites more than 99% of the atoms in an ideal situation to the first and second excited bands within 100 $\ensuremath{\mu}\mathrm{s}$. Our main finding is that the system permitting the Dirac point possesses a region of parameters where the excited energy bands become nearly parabolic, conducive to a robust wave packet with high coherence and isochronicity. We also provide an appropriate data set for future experimentation, including effects of the atom-atom interaction by way of the mean-field nonlinear term.