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arXiv 2105.04853cond-mat.str-el
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各向异性自旋团簇上中子非弹性散射的对称性诱导的普遍动量转移相关性

Symmetry-Induced Universal Momentum-Transfer Dependencies for Inelastic Neutron Scattering on Anisotropic Spin Clusters

Shadan Ghassemi Tabrizi

摘要:

非弹性中子散射(INS)是研究自旋系统(包括分子自旋团簇)磁激发的重要方法。该方法在最近几年有了显著的进步,现在允许探测作为能量传递和动量传递矢量Q的函数的散射强度。最近的研究表明,高分子对称性有利于光谱分析。点群对称性在各向同性和各向异性自旋模型中施加了选择规则。此外,INS强度的Q依赖性可以完全由转变中所涉及的状态的点群对称性确定,从而提供动力学(能量、转变强度)和几何特征(Q依赖性)的清楚分离。目前的工作解决这个问题的各向异性自旋模型。我们确定了一些情况下,Q依赖性是完全固定的点群对称性。对于六元和八元平面自旋环和两个多面体(立方体和二十面体),我们列表并绘制相应的粉末平均普适强度函数。概述的形式主义直接适用于其他高度对称的系统,并应是有用的INS光谱的未来分析的重点放在那些功能,包含信息的自旋动力学或点群对称的状态。

英文摘要:

Inelastic neutron scattering (INS) is a key method for studying magnetic excitations in spin systems, including molecular spin clusters. The method has significantly advanced in recent years and now permits to probe the scattering intensity as a function of the energy transfer and the momentum-transfer vector Q. It was recently shown that high molecular symmetry facilitates the analysis of spectra. Point-group symmetry imposes selection rules in isotropic as well as anisotropic spin models. Furthermore, the Q-dependence of the INS intensity may be completely determined by the point-group symmetry of the states involved in a transition, thereby affording a clear separation of dynamics (energies, transition strengths) and geometrical features (Q-dependencies). The present work addresses this issue for anisotropic spin models. We identify a number of cases where the Q-dependence is completely fixed by the point-group symmetry. For six- and eight-membered planar spin rings and two polyhedra (the cube and the icosahedron) we tabulate and plot the corresponding powder-averaged universal intensity functions. The outlined formalism straightforwardly applies to other highly-symmetric systems and should be useful for future analyses of INS spectra by focusing on those features that contain information on either spin dynamics or the point-group symmetry of states.

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