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arXiv 1912.04463cond-mat.stat-mech
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三维晶格上混合自旋Blume-Capel模型中三临界点的自旋依赖性:Metropolis和Wang-Landau抽样方法

Spin dependence of the tricritical point in the mixed-spin Blume-Capel model on three-dimensional lattices: Metropolis and Wang-Landau sampling approaches

Mouhcine Azhari, Unjong Yu

摘要:

利用Metropolis和Wang-Landau蒙特卡罗方法研究了单离子分裂晶体场($Δ$)的简立方晶格和体心立方晶格上自旋为1/2和自旋为$S$的混合自旋Blume-Capel模型($S=1$,$2$和$3$).通过数值模拟,我们证明了三临界点是自旋无关的两个晶格。对于简单立方晶格和体心立方晶格,相图中三临界点的位置分别确定为($Δ_t/J=2.978(1)$ ; $k_B T_t/J=0.439(1)$)和($Δ_t/J=3.949(1)$ ; $k_B T_t/J=0.854(1)$)。一个非常强大的超临界减速和滞后,观察到在大都会更新接近一阶跃迁$Δ>Δ_t$。此外,对于两个晶格,我们发现了一条补偿点线,其中两个子晶格磁化强度具有相同的幅度。我们发现,补偿线也是自旋无关的。

英文摘要:

We investigate the mixed-spin Blume-Capel model with spin-1/2 and spin-$S$ ($S=1$, $2$, and $3$) on the simple cubic and body-centered cubic lattices with single-ion-splitting crystal-field ($Δ$) by using the Metropolis and the Wang-Landau Monte Carlo methods. By numerical simulations, we prove that the tricritical point is spin-independent for both lattices. The positions of the tricritical point in the phase diagram are determined as ($Δ_t/J=2.978(1)$; $k_B T_t/J=0.439(1)$) and ($Δ_t/J=3.949(1)$; $k_B T_t/J=0.854(1)$) for the simple cubic and the body-centered cubic lattices, respectively. A very strong supercritical slowing down and hysteresis were observed in the Metropolis update close to first-order transitions for $Δ>Δ_t$. In addition, for both lattices we found a line of compensation points, where the two sublattice magnetizations have the same magnitude. We show that the compensation lines are also spin-independent.

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