Department of Physics, Tunghai University, Taichung 40704, Taiwan.
J Phys Condens Matter. 2010 May 12;22(18):185601. doi: 10.1088/0953-8984/22/18/185601. Epub 2010 Apr 20.
We numerically study the ground state phase diagram of the two-dimensional hard-core Bose-Hubbard model with nearest-(V(1)) and next-nearest-neighbour (V(2)) repulsions. In particular, we focus on the quarter-filled phases where one supersolid and two solid phases are observed. Using both canonical and grand canonical quantum Monte Carlo (QMC) methods and a mean-field calculation, we provide evidence for the existence of a commensurate supersolid. Despite the two possible diagonal long-range orderings for the solid phase, only one kind of supersolid phase is found to be energetically stable. The competition between the two solid phases manifests itself as a first-order phase transition around 2V(2) ∼ V(1). The change of order parameters as a function of the chemical potential is also presented.
我们通过数值研究了具有最近邻（V(1)）和次近邻（V(2)）排斥的二维硬芯玻色-哈伯德模型的基态相图。特别关注在四分之一填充相位中观察到的一个超固体和两个固体相。使用正则和巨正则量子蒙特卡罗（QMC）方法以及平均场计算，我们提供了存在准超固体的证据。尽管固体相有两种可能的对角长程有序，但是只发现一种超固体相在能量上是稳定的。两种固体相之间的竞争表现为在 2V(2) ∼ V(1)左右的一级相变。还给出了作为化学势函数的序参数的变化。
