Resonant inelastic x-ray scattering (RIXS) is a powerful probe of elementary excitations in solids. It is now widely applied to study magnetic excitations. However, its complex cross section means that RIXS has been more difficult to interpret than inelastic neutron scattering (INS). Here we report $\sim 37$ meV resolution RIXS measurements of the magnetic excitations in ${\mathrm{La}}_2{\mathrm{CuO}}_4$, the antiferromagnetic parent of one system of high-temperature superconductors. At high energies ($\sim 2$ eV), the RIXS spectra show angular-dependent $dd$ orbital excitations in agreement with previous RIXS studies but show new structure. They are interpreted with single-site multiplet calculations. At low energies ($\lesssim 0.3$ eV), we model the wave-vector-dependent single magnon RIXS intensity as the product of the calculated single-ion spin-flip RIXS cross section and the dynamical structure factor $S(\mathbf{Q},\omega )$ of the spin-wave excitations. When $S(\mathbf{Q},\omega )$ is extracted from our data, the wave-vector-dependence of the single-magnon pole intensity shows a similar variation to that observed by INS. Our results confirm that suitably corrected RIXS data can yield the genuine wave-vector and energy dependence of $S(\mathbf{Q},\omega )$ for a cuprate antiferromagnet. In addition to spin waves, our data show structured multimagnon excitations with dispersing peaks in the intensity at energies higher than the single-magnon excitations.

中文翻译：

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通过共振非弹性 X 射线散射研究 La2CuO4 中的动态自旋磁化率

共振非弹性 X 射线散射 (RIXS) 是一种强大的固体元素激发探测器。它现在被广泛应用于研究磁激发。然而，其复杂的横截面意味着 RIXS 比非弹性中子散射 (INS) 更难以解释。我们在这里报道$～37$ 磁激发的 meV 分辨率 RIXS 测量 ${拉}_2{\mathrm{氧化铜}}_4$，一个高温超导体系统的反铁磁母体。在高能量（$～2$ eV)，RIXS 光谱显示角度依赖 $dd$轨道激发与之前的 RIXS 研究一致，但显示出新的结构。它们通过单点多重计算进行解释。在低能量（$\lesssim 0.3$ eV)，我们将依赖波矢量的单磁振子 RIXS 强度建模为计算的单离子自旋翻转 RIXS 横截面和动力学结构因子的乘积 $秒(\mathbf{问},\omega )$自旋波激发。什么时候$秒(\mathbf{问},\omega )$从我们的数据中提取，单磁振子强度的波矢依赖性显示出与 INS 观察到的相似变化。我们的结果证实，适当校正的 RIXS 数据可以产生真正的波矢量和能量依赖性$秒(\mathbf{问},\omega )$对于铜酸盐反铁磁体。除了自旋波，我们的数据还显示了结构化的多磁振子激发，其强度的色散峰值高于单磁振子激发的能量。