Superfluidity of Bose–Einstein condensate in an optical lattice: Landau–Zener tunnelling and dynamical instability
Superfluidity of Bose–Einstein condensate in an optical lattice: Landau–Zener tunnelling and dynamical instability
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DOI：
10.1088/1367-2630/5/1/104
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发表时间：
2003-06
影响因子：
3.3
通讯作者：
Biao Wu;Q. Niu
中科院分区：
文献类型：
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作者：
Biao Wu;Q. Niu
光学晶格中玻色-爱因斯坦凝聚体的超流可以用布洛赫波来表示，布洛赫波是一种具有周期性振幅调制的平面波。我们回顾了Bloch波的能量色散和线性稳定性中的相互作用效应的理论结果。当原子间的排斥力足够强时，最低的布洛赫带会在布里渊区的边缘形成一个环，即使在外力消失的极限下，朗道-齐纳隧穿的概率也是有限的。超流性可以存在于布里渊区的中心区域，在存在排斥相互作用的情况下，超过排斥相互作用，朗道不稳定性发生，其中系统可以通过过渡到具有较小布洛赫波数的状态来降低其能量。在朗道不稳定区域的外部，布洛赫波也是动态不稳定的，在这个意义上，一个小的初始偏差随时间呈指数增长。在朗道不稳定性的内部区域，布洛赫波在没有持续外部扰动的情况下是动态稳定的。我们的研究结果的实验意义将被讨论。
Superflow of a Bose–Einstein condensate in an optical lattice is represented by a Bloch wave, a plane wave with periodic modulation of the amplitude. We review the theoretical results of the interaction effects in the energy dispersion of the Bloch waves and in the linear stability of such waves. For sufficiently strong repulsion between the atoms, the lowest Bloch band develops a loop at the edge of the Brillouin zone, with the dramatic consequence of a finite probability of Landau–Zener tunnelling even in the limit of a vanishing external force. Superfluidity can exist in the central region of the Brillouin zone in the presence of a repulsive interaction, beyond which Landau instability takes place where the system can lower its energy by making a transition into states with smaller Bloch wavenumbers. In the outer part of the region of Landau instability, the Bloch waves are also dynamically unstable in the sense that a small initial deviation grows exponentially in time. In the inner region of Landau instability, a Bloch wave is dynamically stable in the absence of persistent external perturbations. Experimental implications of our findings will be discussed.