Lin Y-J, Compton R L, Jiménez-García K, Porto J V, Spielman I B
Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, Maryland, 20899, USA.
Nature. 2009 Dec 3;462(7273):628-32. doi: 10.1038/nature08609.
Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation-a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall effect in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, which is evident from the appearance of vortices in our Bose-Einstein condensate. Our approach uses a spatially dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems. With a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation.
中性原子玻色凝聚体和简并费米气体已被用于以最简单和最基本的形式实现重要的多体现象，而没有许多通常与材料系统相关的复杂性。然而，这些系统的电荷中性存在明显的局限性——对于磁场中带电粒子的洛伦兹力会产生一系列有趣的现象，例如二维电子系统中的分数量子霍尔效应。可以通过利用洛伦兹力和科里奥利力的等效性在旋转的中性系统中创建合成磁场来规避这一局限性。这在旋转量子气体的开创性实验中通过量化涡旋的出现得到了证明，这是磁场中超流体或超导体的一个标志。然而，由于技术问题限制了最大旋转速度、旋转状态的亚稳态性质以及应用稳定旋转光学晶格的困难，旋转方法无法达到量子霍尔物理所需的大磁场。在这里，我们通过实验实现了一种用于超冷中性原子的光学合成磁场，这从我们的玻色 - 爱因斯坦凝聚体中涡旋的出现可以明显看出。我们的方法利用了原子内部状态之间空间相关的光学耦合，产生足以创建大合成磁场的贝里相位，并且不受旋转系统的限制。通过合适的晶格配置，应该有可能达到量子霍尔区域，从而有可能实现对拓扑量子计算的研究。
