To elucidate the spin dynamics of La$_{2-x}$Sr$_x$CuO$_4$, which couples with the charge degree of freedom, the spin excitations spanning the characteristic energy ($E_{\rm cross}$ $\sim$35-40 meV) are investigated for underdoped $x$ = 0.10 and optimally doped (OP) $x$ = 0.16 through inelastic neutron scattering measurements. Analysis based on a two-component picture of high-quality data clarified the possible coexistence of uprightly standing incommensurate (IC) excitations with gapless commensurate (C) excitations in the energy-momentum space. The IC component weakens the intensity toward $E_{\rm cross}$ with increasing energy transfer ($\hbar\omega$), whereas the C component strengthens at high-$\hbar\omega$ regions. The analysis results imply that the superposition of two components with a particular intensity balance forms an hourglass-shaped excitation in appearance. Furthermore, the temperature dependence of the intensity of each component exhibits different behaviors; the IC component disappears near the pseudo-gap temperature ($T$*) upon warming, whereas the C component is robust against temperature. These results suggest the itinerant electron spin nature and the localized magnetism of the parent La$_2$CuO$_4$ in IC and C excitations, respectively, similar to the spin excitations in the OP YBa$_2$Cu$_3$O$_{6+\delta}$ and HgBa$_2$CuO$_{4+\delta}$ with higher superconducting-transition temperatures.

中文翻译：

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La2−xSrxCuO4 (x = 0.10 和 0.16) 磁激发中两种成分的共存

为了阐明与电荷自由度耦合的 La$_{2-x}$Sr$_x$CuO$_4$ 的自旋动力学，跨越特征能量的自旋激发（$E_{\rm cross}$ $ \sim$35-40 meV) 通过非弹性中子散射测量研究了欠掺杂 $x$ = 0.10 和最佳掺杂 (OP) $x$ = 0.16。基于高质量数据的双分量图片的分析阐明了能量-动量空间中直立不公度 (IC) 激发与无间隙相称 (C) 激发可能共存的情况。IC 分量随着能量转移（$\hbar\omega$）的增加而减弱了向 $E_{\rm cross}$ 的强度，而 C 分量在高 $\hbar\omega$ 区域增强。分析结果表明，具有特定强度平衡的两个分量的叠加在外观上形成了沙漏形激发。此外，每个组件强度的温度依赖性表现出不同的行为；IC 组件在升温后在伪间隙温度 ($T$*) 附近消失，而 C 组件对温度具有鲁棒性。这些结果表明，IC 和 C 激发中的母体 La$_2$CuO$_4$ 的流动电子自旋性质和局部磁性，分别类似于 OP YBa$_2$Cu$_3$O$_ 中的自旋激发{6+\delta}$ 和 HgBa$_2$CuO$_{4+\delta}$ 具有更高的超导转变温度。IC 组件在升温后在伪间隙温度 ($T$*) 附近消失，而 C 组件对温度具有鲁棒性。这些结果表明，IC 和 C 激发中的母体 La$_2$CuO$_4$ 的流动电子自旋性质和局部磁性分别类似于 OP YBa$_2$Cu$_3$O$_ 中的自旋激发{6+\delta}$ 和 HgBa$_2$CuO$_{4+\delta}$ 具有更高的超导转变温度。IC 组件在升温后在伪间隙温度 ($T$*) 附近消失，而 C 组件对温度具有鲁棒性。这些结果表明，IC 和 C 激发中的母体 La$_2$CuO$_4$ 的流动电子自旋性质和局部磁性分别类似于 OP YBa$_2$Cu$_3$O$_ 中的自旋激发{6+\delta}$ 和 HgBa$_2$CuO$_{4+\delta}$ 具有更高的超导转变温度。