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Spin diffusion in anisotropic Heisenberg chains: S≥1/2

机译:各向异性海森堡链中的自旋扩散:S≥1/ 2

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摘要

In this paper, we investigate spin diffusion in Heisenberg chains with uniaxial nearest-neighbor interactions. The approach followed is based on an analysis of the infinite-temperature longitudinal spin density and spin current correlation functions. For S=1/2, exact results are presented for the time-dependent correlation functions in the XY limit. Away from this limit, the second and fourth moments of the Fourier transform of the spin density correlation function provide information about spin dynamics for arbitrary values of the spin. The moments are used in an assessment of the accuracy of the Gaussian approximation for the spin diffusion constant for S=1/2. The general behavior of the Gaussian approximation when S>1/2 is discussed, and numerical results for the spin diffusion constant are presented for S=1/2, 1, 3/2, 2 and in the classical limit. A moment-based criterion for the boundary in reciprocal space between diffusive and non-diffusive dynamics that applies to arbitrary values of the spin is presented.
机译:在本文中,我们研究了具有单轴最近邻相互作用的海森堡链中的自旋扩散。所采用的方法基于对无限温度纵向自旋密度和自旋电流相关函数的分析。对于S = 1/2,将给出XY极限中时间相关函数的精确结果。远离此限制,自旋密度相关函数的傅立叶变换的第二和第四矩提供了有关自旋任意值的自旋动力学的信息。这些力矩用于评估S = 1/2时自旋扩散常数的高斯近似精度。讨论了当S> 1/2时高斯近似的一般行为,并给出了在S = 1 / 2、1、3 / 2、2和经典极限下自旋扩散常数的数值结果。提出了基于矩的准则,该准则适用于扩散和非扩散动力学之间的倒数空间中的边界,该边界适用于自旋的任意值。

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