Charge density wave (CDW) in high-T_C cuprates has drawn a lot of attention in the field. In this article, we review some of our recent x-ray studies about the ground state and the excitation spectrum of the CDW. Using high magnetic field to suppress the superconductivity, a three-dimensionally-ordered charge stripe state emerges in YBa₂Cu₃O_6+x at low temperatures, which arguably bears the characteristics of the CDW ground state. Regarding excitation spectrum, we utilized the state-of-the-art soft x-ray resonant inelastic scattering (RIXS) and found signatures of dispersive CDW excitations which manifest as some form of interference with the RIXS phonon excitations. This observation provides a new perspective to study the relationship between the CDW, the superconductivity and the putative quantum criticality inside the superconducting dome of the cuprate phase diagram. Within this context, relevant recent experimental studies are also briefly discussed.

中文翻译：

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CDW 基态的 X 射线研究和高 TC 铜酸盐中的激发

高T _C铜酸盐中的电荷密度波 (CDW)引起了该领域的广泛关注。在本文中，我们回顾了我们最近关于基态和 CDW 激发光谱的一些 X 射线研究。利用强磁场抑制超导性，YBa ₂ Cu ₃ O _{6+ x 中}出现三维有序电荷条纹态在低温下，这可以说具有 CDW 基态的特征。关于激发光谱，我们利用了最先进的软 X 射线共振非弹性散射 (RIXS) 并发现了色散 CDW 激发的特征，这些特征表现为对 RIXS 声子激发的某种形式的干扰。这一观察为研究铜酸盐相图的超导圆顶内的 CDW、超导性和假定的量子临界性之间的关系提供了新的视角。在此背景下，还简要讨论了相关的近期实验研究。