关联电子材料中磁激发的非弹性中子和X射线散射探测

Probing magnetic excitations in correlated electron materials using inelastic neutron and X-ray scattering

在关联电子体系中,多种形式的磁性相互作用可能会诱导产生丰富的磁性基态,包括反铁磁莫特绝缘体、反铁磁洪特金属、量子自旋液体、低维量子磁体等.为了理解这些基态产生的微观机制及相关物理,首先需要测量其中的磁激发,通过对磁激发的动力学结构因子进行理论建模和分析可以获得其中自旋-自旋相互作用的详细信息.目前,人们已经发展了多种实验技术来测量磁性体系中的自旋动力学.在这些探测手段中,非弹性中子散射(Inelastic Neutron Scattering,INS)和共振非弹性X射线散射(Resonant Inelastic X-ray Scattering,RIXS),已经被证明是在大范围动量和能量空间中测量磁激发的最有力的、互补的两种实验手段.INS测量磁激发在理论和实验方面都已经发展得相当成熟,但实验中通常需要大量的单晶样品,而RIXS是一种正在快速发展的实验技术,最大的优点之一是可以测量包括薄膜和异质结在内的很小的单晶样品.在本文中,我们主要讨论了INS和RIXS在研究几类典型强关联材料时的比较和互补性.INS和RIXS结合将使我们能够测量包含低维材料在内的几乎所有磁性关联电子材料中的磁激发,进而促进这些材料中关键科学问题的最终解决.

In correlated electron systems,magnetic interactions in various forms can yield rich exotic magnetic ground states including antiferromagnetic Mott insulator,antiferromagnetic Hund’s metal,quantum spin liquid,low-dimensional quantum magnets,and topological magnets.To understand the microscopic mechanism and underlying physics of these materials,it is essential to probe the magnetic excitations and obtain detailed information about the spin-spin interactions by modeling the dynamical structure factor of the spin excitations.Although several techniques have been developed to measure the spin dynamics of magnetic systems,inelastic neutron scattering(INS)and resonant inelastic X-ray scattering(RIXS)have proven to be powerful and complementary probes in mapping the elementary magnetic excitations over a wide energy and momentum range.Furthermore,INS is a well-established technique requiring a large sample volume,whereas RIXS is a fast-developing method that can measure small crystals,including thin films and heterostructure samples,with high efficiency.This review focuses on discussing the comparison and combination of INS and RIXS in measuring the magnetic excitations of several prototypical correlated electron materials,demonstrating that combining INS and RIXS enables us to study the magnetic excitations in almost all magnetic correlated electron systems,including low-dimensional materials.