Kato Shinya, Inaba Kensuke, Sugawa Seiji, Shibata Kosuke, Yamamoto Ryuta, Yamashita Makoto, Takahashi Yoshiro
Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
NTT Basic Research Laboratories, NTT Corporation, Atsugi 243-0198, Japan.
Nat Commun. 2016 Apr 20;7:11341. doi: 10.1038/ncomms11341.
A system of ultracold atoms in an optical lattice has been regarded as an ideal quantum simulator for a Hubbard model with extremely high controllability of the system parameters. While making use of the controllability, a comprehensive measurement across the weakly to strongly interacting regimes in the Hubbard model to discuss the quantum many-body state is still limited. Here we observe a great change in the excitation energy spectra across the two regimes in an atomic Bose-Hubbard system by using a spectroscopic technique, which can resolve the site occupancy in the lattice. By quantitatively comparing the observed spectra and numerical simulations based on sum rule relations and a binary fluid treatment under a finite temperature Gutzwiller approximation, we show that the spectra reflect the coexistence of a delocalized superfluid state and a localized insulating state across the two regimes.
光学晶格中的超冷原子系统被视为用于哈伯德模型的理想量子模拟器，其系统参数具有极高的可控性。虽然利用了这种可控性，但对哈伯德模型中从弱相互作用到强相互作用区域进行全面测量以讨论量子多体状态仍很有限。在此，我们通过使用一种光谱技术观察到原子玻色 - 哈伯德系统中跨越这两个区域的激发能谱发生了巨大变化，该技术能够分辨晶格中的格点占据情况。通过基于和规则关系以及有限温度下古兹维勒近似下的二元流体处理，对观测光谱与数值模拟进行定量比较，我们表明这些光谱反映了跨越这两个区域的离域超流态和局域绝缘态的共存。
