论文标题
量子群集变量方法和量子铁磁的相图$ J_1 $ - $ J_2 $模型
The Quantum Cluster Variational Method and the Phase Diagram of the quantum ferromagnetic $J_1$-$J_2$ model
论文作者
论文摘要
我们利用量子群集变量方法（QCVM）来研究$ j_1 $ - $ j_2 $用于量子iSing旋转的型号。我们首先描述QCVM并讨论与其他平均场近似值的相关性。在方形晶格中以kikuchi近似的水平研究了模型的相图，这是$ g = j_2/j_1 $，温度和纵向和横向外部场的比率的函数。我们的结果表明，量子波动可能会改变过渡的顺序，并引起铁磁和条纹阶段之间的差距。此外，当存在纵向和横向场时，热波动和量子效应有助于列相位的出现。
We exploit the Quantum Cluster Variational Method (QCVM) to study the $J_1$-$J_2$ model for quantum Ising spins. We first describe the QCVM and discuss how it is related to other Mean Field approximations. The phase diagram of the model is studied at the level of the Kikuchi approximation in square lattices as a function of the ratio between $g = J_2/J_1$ , the temperature and the longitudinal and transverse external fields. Our results show that quantum fluctuations may change the order of the transition and induce a gap between the ferromagnetic and the stripe phases. Moreover, when both longitudinal and transverse fields are present, thermal fluctuations and quantum effects contribute to the appearance of a nematic phase.
