We investigate the effect of magnon-magnon interactions on the dispersion and polarization of magnons in collinear antiferromagnetic (AF) insulators at finite temperatures. In two-sublattice AF systems with either uniaxial or biaxial magnetocrystalline anisotropies, we implement a self-consistent Hartree-Fock mean-field approximation to explore the nonlinear thermal interactions. The resulting nonlinear magnon interactions separate into two-magnon intra- and interband scattering processes. Furthermore, we compute the temperature dependence of the magnon bandgap and AF resonance modes due to nonlinear magnon interactions for square and hexagonal lattices. In addition, we study the effect of magnon interactions on the polarization of magnon modes. We find that although the noninteracting eigenmodes in the uniaxial case are circularly polarized, but in the presence of nonlinear thermal interactions the local U(1) symmetry of the Hamiltonian is broken. The attractive nonlinear interactions squeeze the low-energy magnon modes and make them elliptical. In the biaxial case, on the other hand, the bare eigenmodes of low energy magnons are elliptically polarized but thermal nonlinear interactions squeeze them further. Direct measurements of the predicted temperature-dependent AF resonance modes and their polarization can be used as a tool to probe the nonlinear interactions. Our findings establish a framework for exploring the effect of thermal magnon interactions in technologically important magnetic systems, such as magnetic stability of recently discovered two-dimensional magnetic materials, coherent transport of magnons, Bose-Einstein condensation of magnons, and magnonic topological insulators.
Unidirectional magnetoresistance driven by nonequilibrium antiferromagnetic magnons
South China University of Technology（华南理工大学）；Norwegian University of Science and Technology（挪威科技大学）；Peking University（北京大学）；Nanyang Technological University（南洋理工大学）
Exceptional sign changes of the non-local spin Seebeck effect in antiferromagnetic hematite
基于纯磁振子自旋电流在反铁磁绝缘体材料中传播的低功率自旋电子器件提供了优于铁磁组件的几个明显优点，包括更高频率的磁振子和抗干扰外部磁场的稳定性。在这项工作中，我们利用铁氧化物的绝缘反铁磁相，赤铁矿$α$ -Fe $_2$ O $_3$来研究热产生的磁振子自旋电流的长距离输运。我们报告的自旋Seebeck效应产生的磁振子的激发，平行和垂直于反铁磁易轴下施加的磁场运输。利用原子的赤铁矿玩具模型，我们计算了输运特性的反铁磁有序的偏离平衡下施加的电场。我们解决的作用的磁序参量的运输，实验中，我们发现显着的热自旋运输，而不需要一个净磁化。
Observation of Dyakonov-Perel-type magnon spin relaxation in uniaxial antiferromagnetic insulators
Southern University of Science and Technology（南方科技大学）；Quantum Science Center of Guangdong–Hong Kong–Macao Greater Bay Area (Guangdong)（粤港澳大湾区量子科学中心（广东））；Beijing Normal University（北京师范大学）；Fudan University（复旦大学）
Magnons in antiferromagnetic bcc-Cr and Cr$_2$O$_3$ from time-dependent density functional theory
我们应用含时密度泛函理论计算了bcc-Cr和Cr $_2$ O $_3$的横向磁化率，它们分别构成了具有巡回和局域磁矩的反铁磁体的典型例子。交换相关核被重新缩放，以执行戈德斯通条件和磁振子色散关系的基础上提取的对称性分析依赖于广义Onsager关系。这样做，我们的计算产生的特征线性磁振子色散的反铁磁体在长波长的限制。在Cr $_2$ O $_3$的情况下，我们发现，绝热局域密度近似产生一个很好的定性与测量的色散协议，但高估的磁振子速度和带宽的一个因素。包括哈伯德修正提高了磁振子的速度，但在与实验磁振子色散的整体定性协议的代价。对于体心立方铬，我们发现一个尖锐的声学磁振子模式在低能量与以前报道的值一致的速度。在较高的能量下，声磁振子模式变得受到强烈的朗道阻尼，一旦进入Stoner连续谱就迅速消失。除了声磁振子模式，我们还观察到一个额外的集体模式沿$Γ\rightarrow\mathrm{R}$方向的能量为$\sim$ 1 eV，这是位于内部的斯通纳连续，但似乎逃避朗道阻尼的效果。
Thickness-dependent magnon spin transport in antiferromagnetic insulators: Crossover from quasi-three-dimensional to quasi-two-dimensional regimes
Norwegian University of Science and Technology（挪威科技大学）；Eindhoven University of Technology（埃因霍温理工大学）；ENSTA, Institut Polytechnique de Paris（巴黎理工学院 ENSTA）
Nonreciprocal Magnon Hanle Effect in Antiferromagnetic $α$-Fe$_2$O$_3$
Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften（瓦尔特·迈斯纳研究所，巴伐利亚科学院）；TUM School of Natural Sciences, Technische Universität München（慕尼黑工业大学自然科学学院）；Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid（马德里自治大学凝聚态物理中心（IFIMAC）和凝聚态物质理论物理系）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
Finite-Momentum Antiferromagnetic Magnon Dynamics across the Morin Transition in Hematite
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University（南京大学固体微结构物理国家重点实验室和物理学院）；Jiangsu Physical Science Research Center, Nanjing University（南京大学江苏物理科学研究中心）
Tunable Ultrastrong Magnon-Magnon Coupling and Squeezed States in a Triaxial Van der Waals Antiferromagnet
National Key Laboratory of Spintronics and School of Physics, Nanjing University（南京大学自旋电子学国家重点实验室和物理学院）；School of Science, Nanjing University of Posts and Telecommunications（南京邮电大学理学院）；Laboratory of Solid State Microstructures, Nanjing University（南京大学固体微结构实验室）；State Key Laboratory of Spintronics, Nanjing University（南京大学自旋电子学国家重点实验室）
Plaid-Like Spin Splitting and Chirality of Magnon Bands in Antiferromagnetic MnTe$_2$
Sejong University（世宗大学）；Korea Advanced Institute of Science and Technology (KAIST)（韩国科学技术院）；Sungkyunkwan University（成均馆大学）；Institute of Physics, Academia Sinica（中央研究院物理研究所）
