Multimagnon dynamics and thermalization in the S=1 easy-axis ferromagnetic chain
Multimagnon dynamics and thermalization in the S=1 easy-axis ferromagnetic chain
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DOI：
10.1103/physrevb.105.054413
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发表时间：
2021-07
影响因子：
3.7
通讯作者：
Prakash C. Sharma;Kyun-Jin Lee;Hitesh J. Changlani
中科院分区：
文献类型：
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作者：
Prakash C. Sharma;Kyun-Jin Lee;Hitesh J. Changlani
准粒子是物理驱动的数学结构，用于简化看似复杂的固体多体描述。全面了解它们的动力学以及它们之间有效相互作用的本质，可以提供有关微观层面上真实材料特性的丰富信息。在这项工作中，我们探索了具有易轴现场各向异性的铁磁自旋 1 海森堡链中磁振子准粒子的动力学和相互作用，这是一个与解释最近 NiNb$_2$O$_6$ 太赫兹光学实验相关的模型 [P. Chauhan 等人，物理学。莱特牧师。 124, 037203 (2020)]，以及超冷原子环境中的非平衡动力学 [W.C.钟等人，物理学。莱特牧师。 126, 163203 (2021)]。我们借助由物理驱动的贾斯特罗波函数支持的精确对角化和密度矩阵重整化群计算，构建了一些磁振子云的特性图。我们展示了磁振子的结合能如何随着其数量而有效减少，并解释了这种能量尺度如何与动态磁化率测量直接相关。这种理解用于对超冷原子平台进行预测，该平台非常适合研究多磁子态的热化。我们使用基于矩阵积状态的时间演化块抽取算法来模拟这些链的非平衡动力学，并探索复兴和热化对磁振子密度和易轴现场各向异性（控制有效磁振子相互作用的强度）的依赖性。我们观察到的行为类似于报道的多体量子疤痕的行为，我们用在小各向异性极限下准确的解析近似来解释这种行为。
Quasiparticles are physically motivated mathematical constructs for simplifying the seemingly complicated many-body description of solids. A complete understanding of their dynamics and the nature of the effective interactions between them provides rich information on real material properties at the microscopic level. In this work, we explore the dynamics and interactions of magnon quasiparticles in a ferromagnetic spin-1 Heisenberg chain with easy-axis onsite anisotropy, a model relevant for the explanation of recent terahertz optics experiments on NiNb$_2$O$_6$ [P. Chauhan et al., Phys. Rev. Lett. 124, 037203 (2020)],and nonequilibrium dynamics in ultracold atomic settings [W.C. Chung et al., Phys. Rev. Lett. 126, 163203 (2021)]. We build a picture for the properties of clouds of a few magnons with the help of exact diagonalization and density matrix renormalization group calculations supported by physically motivated Jastrow wavefunctions. We show how the binding energy of magnons effectively reduces with their number and explain how this energy scale is of direct relevance for dynamical magnetic susceptibility measurements. This understanding is used to make predictions for ultracold-atomic platforms which are ideally suited to study the thermalization of multimagnon states. We simulate the nonequilibrium dynamics of these chains using the matrix product state based time-evolution block decimation algorithm and explore the dependence of revivals and thermalization on magnon density and easy-axis onsite anisotropy (which controls the strength of effective magnon interactions). We observe behaviors akin to those reported for many-body quantum scars which we explain with an analytic approximation that is accurate in the limit of small anisotropy.