Hidden topological transitions in emergent magnetic monopole lattices
Hidden topological transitions in emergent magnetic monopole lattices
复制标题
新兴磁单极晶格中隐藏的拓扑转变
DOI：
10.1103/physrevb.107.094437
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发表时间：
2023
影响因子：
3.7
通讯作者：
Motome Yukitoshi
中科院分区：
文献类型：
--
作者：
Kato Yasuyuki;Motome Yukitoshi
被称为磁刺猬的拓扑缺陷实现了麦克斯韦方程组所描述的普通电磁学中不允许出现的突发性磁单极子。这种单极子在实验中以两种不同的形式被发现：四面体晶格和立方刺猬晶格。自旋织构由化学成分、外加磁场和温度调制，通过磁单极子的运动和对湮灭导致量子输运和光学现象，但理论上的理解仍然难以捉摸，特别是在不同类型的刺猬晶格竞争的区域。在这里，我们提出了一个理论模型，可以稳定四面体和立方刺猬晶格，并在改变相互作用参数、磁场和温度的情况下，通过使用最近开发的方法，在热力学极限下提供精确的解决方案，对相图进行了彻底的研究。我们发现，随着单极子和反单极子密度的变化，模型表现出各种类型的拓扑跃迁，其中一些伴随着热力学量的奇点，而另一些则隐藏在很少或没有异常的情况下。我们还发现了三维系统中二维涡旋对湮没的另一种隐藏拓扑跃迁。这些结果不仅为理解现有的实验数据提供了有用的信息，而且对磁单极晶格中隐藏拓扑跃迁的识别和突发性电磁的探索提出了挑战。
Topological defects, called magnetic hedgehogs, realize emergent magnetic monopoles, which are not allowed in the ordinary electromagnetism described by Maxwell's equations. Such monopoles were experimentally discovered in magnets in two different forms: tetrahedraland cubichedgehog lattices. The spin textures are modulated by the chemical composition, an applied magnetic field, and temperature, leading to quantum transport and optical phenomena through movement and pair annihilation of magnetic monopoles, but the theoretical understanding remains elusive, especially in the regions where different types of hedgehog lattices are competing. Here we propose a theoretical model that can stabilize both tetrahedral and cubic hedgehog lattices, and perform a thorough investigation of the phase diagram while changing the interaction parameters, magnetic field, and temperature, by using a recently developed method that delivers exact solutions in the thermodynamic limit. We find that the model exhibits various types of topological transitions with changes of the density of monopoles and antimonopoles, some of which are accompanied by singularities in the thermodynamic quantities, while the others are hidden with less or no anomaly. We also find another hidden topological transition with pair annihilation of two-dimensional vortices in the three-dimensional system. These results not only provide useful information for understanding the existing experimental data but also challenge the identification of hidden topological transitions and the exploration of emergent electromagnetism in magnetic monopole lattices.