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arXiv 0908.3514cond-mat.str-el
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星格子上的玻色-哈伯德模型

Bose-Hubbard model on a star lattice

Sergei V. Isakov, K. Sengupta, Yong Baek Kim

摘要:

本文用量子蒙特卡罗模拟和双涡旋理论分析了星格子上具有最近邻跃迁和排斥相互作用的硬核玻色子的玻色-哈伯德模型。我们得到了该模型的相图作为化学势和相对强度的跳跃和相互作用的函数。在强相互作用机制下,我们发现模型在1/2和1/3填充时的Mott相,与正方形、三角形和Kagome晶格上的Mott相相比,是不对称的共振价键(RVB)相,没有密度波序,或者密度波序和RVB序共存.我们还发现,随着跳跃和相互作用的相对强度的增加,量子不变的Mott态发生直接的二阶超流-绝缘体量子相变。我们计算这些过渡的临界指数,并认为使用双涡图片的过渡,当接近通过莫特叶尖,属于倒置XY普遍性类。

英文摘要:

We analyze the Bose-Hubbard model of hardcore bosons with nearest neighbor hopping and repulsive interactions on a star lattice using both quantum Monte Carlo simulation and dual vortex theory. We obtain the phase diagram of this model as a function of the chemical potential and the relative strength of hopping and interaction. In the strong interaction regime, we find that the Mott phases of the model at 1/2 and 1/3 fillings, in contrast to their counterparts on square, triangular, and Kagome lattices, are either translationally invariant resonant valence bond (RVB) phases with no density-wave order or have coexisting density-wave and RVB orders. We also find that upon increasing the relative strength of hopping and interaction, the translationally invariant Mott states undergo direct second order superfluid-insulator quantum phase transitions. We compute the critical exponents for these transitions and argue using the dual vortex picture that the transitions, when approached through the tip of the Mott lobe, belong to the inverted XY universality class.

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