Blume-Capel 模型的相图与转变性质：蒙特卡洛研究

中文摘要 AI 辅助

我们使用蒙特卡洛方法研究了有无外磁场情况下的 Jx-Jy Blume-Capel 模型。我们的目标是验证三临界点的位置，检查重入行为的存在性，并研究这一特定设计系统的磁热性质。在无场情形下，蒙特卡洛模拟给出的临界温度低于常规反铁磁方格。当施加外磁场时，我们在混合态区域观察到一维自发对称破缺相的迹象，这与次级比热峰相矛盾。我们拍摄了该状态的快照，并利用自旋为1的旋量玻色-爱因斯坦凝聚体领域的平均场理论阐明了其潜在机制。关于重入行为，我们确认了当磁场变化时其发生，但仅在温度保持恒定的情况下。在该系统中未识别出依赖于温度的重入行为。最后，我们考察了磁热性质，在所考虑的相变点区域内未发现一级相变的证据。尽管逆磁热效应和直接磁热效应均存在且与混合态相关，但我们确定相关的相变均为二级相变。

英文摘要

The Jx-Jy Blume-Capel model, with and without an external magnetic field, is investigated using the Monte Carlo method. Our aim is to verify the location of the tricritical point, examine the existence of reentrant behavior, and study the magnetocaloric properties of this specifically designed system. In the non-field case, the critical temperature given by the Monte Carlo simulations is lower compared to the conventional antiferromagnetic square lattice. When an external magnetic field is applied, we observed signs of a one-dimensional spontaneous symmetry-breaking phase in the mixed-states regime, which is counterintuitive with secondary specific-heat peak. We take the snapshot of this state and elucidated the underlying mechanisms using mean field theory in the field of spin-1 spinor Bose-Einstein condensate . Regarding reentrant behavior, we confirmed its occurrence as the magnetic field varies, but only when the temperature is kept constant. Temperature-dependent reentrant behavior could not be identified within this system. Finally, we examined the magnetocaloric properties and found no evidence of first-order phase transitions within the region of the considered phase-transition point. Although both inverse and direct magnetocaloric effects are present and related to the mixed state, we identified that the relevant phase transitions are all of the second order.

发表机构

• College of Physics and Optoelectronics, Taiyuan University of Technology（太原理工学院物理与光电工程学院）
• National Institute of Metrology（中国计量科学研究院）

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