We report a comprehensive Cu $L_3$-edge resonant x-ray scattering (RXS) study of two- and three-dimensional (2D and 3D) incommensurate charge correlations in single crystals of the underdoped high-temperature superconductor ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6.67}$ under uniaxial compression up to 1% along the two inequivalent $\mathrm{Cu}─\mathrm{O}─\mathrm{Cu}$ bond directions ($a$ and $b$) in the ${\mathrm{CuO}}_2$ planes. We confirm the strong in-plane anisotropy of the 2D charge correlations and observe their symmetric response to pressure: pressure along $a$ enhances correlations along $b$, and vice versa. Our results imply that the underlying order parameter is uniaxial. In contrast, 3D long-range charge order is only observed along $b$ in response to compression along $a$. Spectroscopic RXS measurements show that the 3D charge order resides exclusively in the ${\mathrm{CuO}}_2$ planes and may thus be generic to the cuprates. We discuss implications of these results for models of electronic nematicity and for the interplay between charge order and superconductivity.

中文翻译：

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单轴压缩下共振X射线散射在YBa2Cu3O6.67中产生的电荷密度波

我们报告了全面的铜 ${\mathrm{大号}}_3$欠掺杂高温超导体单晶中二维和三维（2D和3D）不相称电荷相关性的边缘共振x射线散射（RXS）研究 ${\mathrm{Ba}}_2{铜}_3{\mathrm{Ø}}_{6.67}$ 在单轴压缩下沿两个不等式的最大1％ $铜─\mathrm{Ø}─铜$ 键方向（$\mathrm{一种}$ 和 $b$） 在里面 ${\mathrm{氧化铜}}_2$飞机。我们确认了二维电荷相关性的强平面各向异性，并观察了它们对压力的对称响应：$\mathrm{一种}$ 增强相关性 $b$，反之亦然。我们的结果暗示基本的顺序参数是单轴的。相比之下，仅在$b$ 响应压缩 $\mathrm{一种}$。光谱RXS测量显示3D充电顺序仅存在于${\mathrm{氧化铜}}_2$平面，因此可能对铜价通用。我们讨论了这些结果对电子向列性模型以及电荷阶和超导性之间相互作用的影响。