Parametric Instabilities of Interacting Bosons in Periodically Driven 1D Optical Lattices
Parametric Instabilities of Interacting Bosons in Periodically Driven 1D Optical Lattices
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DOI：
10.1103/physrevx.10.011030
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发表时间：
2018-08
影响因子：
12.5
通讯作者：
Jakob Näger;Karen Wintersperger;Marin Bukov;S. Lellouch;E. Demler;U. Schneider;I. Bloch;N. Goldman;M. Aidelsburger
中科院分区：
文献类型：
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作者：
Jakob Näger;Karen Wintersperger;Marin Bukov;S. Lellouch;E. Demler;U. Schneider;I. Bloch;N. Goldman;M. Aidelsburger
目前，人们正在探索周期性驱动的量子系统，以实现相互作用的拓扑相。这种Floquet工程方法在超冷原子气体中特别有前途，其中拓扑能带结构可以通过精心设计的摇动协议进行工程设计，并且粒子间的相互作用可以进行微调。虽然这两个功能已经单独证明，相互作用和时间周期性驱动之间的相互作用可能会导致不可控的加热和不稳定性，可能会阻止任何实际应用该计划。在这项工作中，我们通过实验确定存在的参数不稳定性，这触发了破坏弱相互作用的玻色-爱因斯坦凝聚在强驱动的光学晶格通过指数增长的集体激发。通过监测的动量分布的时间演化，我们确定这些激发的性质，并证明了横向自由度和谐波陷阱沿着晶格轴所发挥的关键作用。我们确定了最不稳定的集体模式，这是占主导地位的不稳定性，Bogoliubov理论预测。理解驱动量子系统中不稳定性的开始对于确定实现物质强相关拓扑状态的最佳条件至关重要。
Periodically-driven quantum systems are currently explored in view of realizing interacting topological phases. This Floquet-engineering approach is particularly promising in gases of ultracold atoms, where topological band structures can be engineered through well-designed shaking protocols, and where inter-particle interactions can be finely tuned. While both features have been demonstrated individually, the interplay between interactions and time-periodic driving can lead to uncontrollable heating and instabilities, potentially preventing any practical application of this scheme. In this work, we experimentally identify the existence of parametric instabilities, which trigger the destruction of weakly-interacting Bose-Einstein condensates in strongly-driven optical lattices through the exponential growth of collective excitations. By monitoring the time evolution of the momentum distribution, we determine the nature of these excitations and demonstrate the crucial role played by the transverse degrees of freedom and the harmonic trap along the lattice axis. We identify the most unstable collective mode, which is shown to dominate the instability, as predicted by Bogoliubov theory. Understanding the onset of instability in driven quantum systems is crucial for determining optimal conditions for realizing strongly-correlated topological states of matter.