Janus粒子阵列的取向有序性作为经典罗盘自旋系统
Orientational Ordering of Janus Particle Arrays as Classical Compass Spin Systems
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中文总结 AI 辅助
本研究通过经典罗盘模型和Kern--Frenkel模型模拟Janus粒子阵列，揭示六重取向有序源于热序-by-无序，并展示高阶相互作用可改变取向选择，连接微观各向异性与XY涡旋物理。
中文摘要 AI 辅助
Janus粒子阵列提供了一个软物质平台，其中粒子取向作为具有各向异性、键依赖相互作用的经典自旋。受近期关于金属-介电Janus粒子三角形阵列实验的启发，该实验展示了六重取向有序以及可直接观察的涡旋和反涡旋，我们研究了超越各向同性XY描述的有效模型。经典$120^\circ$罗盘模型捕捉了最小键方向相互作用，而有效的Kern--Frenkel模型更直接地结合了Janus表面相互作用的几何形状。蒙特卡洛模拟表明，两种模型均表现出低温六重有序相、高温无序相，以及与两次Berezinskii--Kosterlitz--Thouless转变一致的中间准长程有序区域。在两种情况下，六重有序通过热序-by-无序从连续简并的铁磁流形产生。我们进一步表明，$120^\circ$相互作用的高阶扩展可以改变取向选择：二次项反转了涨落诱导的六重各向异性，而三次项在能量上提升简并性，并选择与实验观察到的晶格对齐方向一致的方向。这些结果将Janus粒子相互作用的微观各向异性与涌现的XY类涡旋物理联系起来，并说明了不同的微观机制如何产生相似的六重取向有序。
英文摘要
Janus-particle arrays provide a soft-matter platform in which particle orientations act as classical spins with anisotropic, bond-dependent interactions. Motivated by recent experiments on triangular arrays of metallodielectric Janus particles exhibiting sixfold orientational order and directly observable vortices and antivortices, we study effective models beyond the isotropic XY description. A classical $120^\circ$ compass model captures the minimal bond-directional interaction, while an effective Kern--Frenkel model incorporates the geometry of the Janus surface interaction more directly. Monte Carlo simulations show that both models exhibit a low-temperature sixfold ordered phase, a high-temperature disordered phase, and an intermediate quasi-long-range-ordered regime consistent with two Berezinskii--Kosterlitz--Thouless transitions. In both cases, the sixfold order arises through thermal order-by-disorder from a continuously degenerate ferromagnetic manifold. We further show that higher-order extensions of the $120^\circ$ interaction can alter the orientational selection: a quadratic term reverses the fluctuation-induced sixfold anisotropy, while a cubic term lifts the degeneracy energetically and selects the lattice-aligned directions that coincide with those observed experimentally. These results connect the microscopic anisotropy of Janus-particle interactions to emergent XY-like vortex physics and illustrate how distinct microscopic mechanisms can produce similar sixfold orientational order.
发表机构
- University of Science and Technology of China（中国科学技术大学）
- Shanghai Research Center for Quantum Science（上海量子科学研究中心）
- CAS Center for Excellence in Quantum Information and Quantum Physics（中国科学院量子信息与量子物理卓越创新中心）
- Hefei National Laboratory（合肥国家实验室）
- Brandeis University（布兰迪斯大学）
- Martin A. Fisher School of Physics, Brandeis University（布兰迪斯大学马丁·A·费舍尔物理学院）
- University of Virginia（弗吉尼亚大学）
- Department of Physics, University of Virginia（弗吉尼亚大学物理系）
- Department of Mathematics, University of Virginia（弗吉尼亚大学数学系）
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