双层镍酸盐La$_{3}$Ni$_{2}$O$_{7}$中自旋密度波（SDW）态的非常规压力演化
Unconventional Pressure Evolution of Spin-Density-Wave State in La$_{3}$Ni$_{2}$O$_{7}$
AI总结：
通过对La$_{3}$Ni$_{2}$O$_{7}$单晶的高压电子拉曼研究，揭示其SDW态在压力下能量尺度增强但长程序减弱的非常规演化，为双层镍酸盐超导相关磁关联提供光谱约束。
AI中文摘要：
双层镍酸盐La$_{3}$Ni$_{2}$O$_{7}$中压力诱导高温超导电性的发现，引发了其自旋密度波（SDW）态如何向超导区演化的问题。本文报道了对La$_{3}$Ni$_{2}$O$_{7}$单晶在最高16.51 GPa静水压下的系统性电子拉曼研究。SDW能隙和转变温度$T_{\text{SDW}}$总体随压力升高而增大，而无量纲耦合比2$\boldsymbol{\text{Δ}}_{\text{SDW}}/(k_{\text{B}}T_{\text{SDW}})$保持在~7.5左右，表明SDW态具有稳定的强耦合特性。同时，施加压力后拉曼SDW峰展宽，说明长程SDW序逐渐减弱。这些结果揭示了一种不寻常的压力演化：SDW能量尺度增强的同时，SDW态的相干性逐渐降低，为双层镍酸盐中与超导电性相关的磁关联提供了光谱学约束。
英文摘要：
The discovery of pressure-induced high temperature superconductivity in the bilayer nickelate La$_{3}$Ni$_{2}$O$_{7}$ has raised the question of how its spin-density-wave (SDW) state evolves toward the superconducting regime. Here, we report a systematic electronic Raman study of La$_{3}$Ni$_{2}$O$_{7}$ single crystals under hydrostatic pressures up to 16.51 GPa. Both the SDW gap energy and the transition temperature $T_{\mathrm{SDW}}$ show an overall increase with pressure, while the dimensionless coupling ratio 2$Δ_{\text{SDW}}/(k_{\text{B}}T_{\text{SDW}})$ remains constant around $\sim7.5$, indicating a robust strong-coupling character of SDW state. At the same time, the Raman SDW peak broadens as pressure is applied, indicating a gradual weakening of long-range SDW order. These results reveal an unusual pressure evolution in which the SDW energy scale is enhanced while the SDW state becomes progressively less coherent, providing spectroscopic constraints on the magnetic correlations relevant to superconductivity in bilayer nickelates.
