We propose a new method to numerically calculate transition points that belongs to 2D Ising universality class for quantum spin models. Generally, near the multicritical point, in conventional methods, a finite size correction becomes very large. To suppress the effect of the multicritical point, we use a z-axis twisted boundary condition and a y-axis twisted boundary condition. We apply our method to an S = 1/2 bond-alternating XXZ model. The multicritical point of this model has a BKT transition, where the correlation length diverges singularly. However, with our method, the convergence of calculation is highly improved, thus we can calculate the transition point even near the multicritical point.

中文翻译：

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一种计算二维伊辛普适性过渡点的新方法：在阿什金-泰勒多临界点附近的应用

我们提出了一种新方法来数值计算属于量子自旋模型的 2D Ising 普适性类的过渡点。通常，在多临界点附近，在常规方法中，有限尺寸校正变得非常大。为了抑制多临界点的影响，我们使用 z 轴扭曲边界条件和 y 轴扭曲边界条件。我们将我们的方法应用于 S = 1/2 键交替 XXZ 模型。该模型的多临界点具有 BKT 过渡，其中相关长度奇异地发散。然而，我们的方法大大提高了计算的收敛性，因此我们甚至可以在多临界点附近计算过渡点。