Phase diagram of the bose-hubbard model with T3 symmetry
Phase diagram of the bose-hubbard model with T3 symmetry
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DOI：
10.1103/physrevb.73.144511
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发表时间：
2005-10
影响因子：
3.7
通讯作者：
M. Rizzi;V. Cataudella;R. Fazio
中科院分区：
文献类型：
--
作者：
M. Rizzi;V. Cataudella;R. Fazio
本文研究了具有T_3结构的Bose-Hubbard模型中绝缘相和全局相干相之间的量子相变。即使在没有阻挫的情况下，超流相的特征也是序参量对T_3结构的不同子晶格的调制。零温临界点随磁场的变化呈典型的“蝴蝶”形。在完全受挫时，超流区域被强烈抑制。此外，由于在f=1/2的Aharonov-Bohm笼的存在，我们发现存在一个中间绝缘相的证据，其特征在于零超流刚度，但有限的压缩性。在这个中间阶段，由于外部阻挫和T_3晶格的拓扑结构，玻色子被局域化。我们将这种新相命名为Aharonov-Bohm（AB）绝缘体。当存在电荷阻挫时，相图呈现典型的瓣状结构。分数填充的Mott绝缘态的形式和层次由T_3晶格的特殊拓扑结构决定。本文中提出的结果是通过各种分析方法：平均场和变分技术接近相边界的超导侧，和一个强耦合的扩展适当的莫特绝缘区。此外，我们进行了相应的（2+1）D XY模型的量子Monte Carlo模拟，以证实更准确的定量分析的解析计算。最后讨论了用光学晶格和约瑟夫森结阵列实现T_3晶格的实验。
In this paper we study the quantum phase transition between the insulating and the globally coherent superfluid phases in the Bose-Hubbard model with T_3 structure, the "dice lattice". Even in the absence of any frustration the superfluid phase is characterized by modulation of the order parameter on the different sublattices of the T_3 structure. The zero-temperature critical point as a function of a magnetic field shows the characteristic "butterfly" form. At fully frustration the superfluid region is strongly suppressed. In addition, due to the existence of the Aharonov-Bohm cages at f=1/2, we find evidence for the existence of an intermediate insulating phase characterized by a zero superfluid stiffness but finite compressibility. In this intermediate phase bosons are localized due to the external frustration and the topology of the T_3 lattice. We name this new phase the Aharonov-Bohm (AB) insulator. In the presence of charge frustration the phase diagram acquires the typical lobe-structure. The form and hierarchy of the Mott insulating states with fractional fillings, is dictated by the particular topology of the T_3 lattice. The results presented in this paper were obtained by a variety of analytical methods: mean-field and variational techniques to approach the phase boundary from the superconducting side, and a strongly coupled expansion appropriate for the Mott insulating region. In addition we performed Quantum Monte Carlo simulations of the corresponding (2+1)D XY model to corroborate the analytical calculations with a more accurate quantitative analysis. We finally discuss experimental realization of the T_3 lattice both with optical lattices and with Josephson junction arrays.