The discovery of a magnetic-field-induced charge-density-wave (CDW) order in the pseudogap state via nuclear magnetic resonance (NMR) studies has highlighted the importance of “charge” in the physics of high transition-temperature (T_c) superconductivity in copper oxides (cuprates). Herein, after briefly reviewing the progress achieved in the last few years, we report new results of ^63,65Cu-NMR measurements on the CDW order and its fluctuation in the single-layered cuprate Bi₂Sr_2−xLa_xCuO_6+δ. The NMR spectrum under both in- and out-of-plane magnetic fields above H = 10 T indicates that the CDW replaces the antiferromagnetic order before superconductivity appears, but disappears before superconductivity is optimized. We found that the CDW onset temperature T_CDW scales with the pseudogap temperature T^*. Comparison between ⁶³Cu and ⁶⁵Cu NMR indicates that the spin–lattice relaxation process is dominated by charge fluctuations in the doping regions where the CDW appears as well as at the pseudogap end point (T^* = 0). These results suggest that charge orders and fluctuations exist in multiple doping regions and over a quite wide temperature range.

中文翻译：

---

63,65Cu-核磁共振揭示的Bi2Sr2−xLaxCuO6+δ中的电荷顺序和波动

通过核磁共振 (NMR) 研究在赝隙态中发现了磁场诱导的电荷密度波 (CDW) 阶次，这凸显了“电荷”在高转变温度 ( T _c )物理学中的重要性铜氧化物（铜酸盐）的超导性。在此，在简要回顾了过去几年取得的进展后，我们报告了^63,65 Cu-NMR 测量 CDW 阶次及其在单层铜酸盐 Bi ₂ Sr _{2− x} La _x CuO _{6+ 中的}波动的新结果_δ。高于H的面内和面外磁场下的核磁共振谱= 10 T 表示 CDW 在超导出现之前取代了反铁磁有序，但在超导优化之前消失。我们发现 CDW 起始温度T _CDW与赝间隙温度T ^{* 成}比例。⁶³ Cu 和⁶⁵ Cu NMR之间的比较表明，自旋-晶格弛豫过程主要由 CDW 出现的掺杂区域以及赝隙端点（T ^* = 0）中的电荷波动主导。这些结果表明电荷顺序和波动存在于多个掺杂区域和相当宽的温度范围内。