Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.; Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.; Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.; Quantum Materials Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada.
School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
Sci Adv. 2016 Aug 12;2(8):e1600782. doi: 10.1126/sciadv.1600782. eCollection 2016 Aug.
Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2-x Ce x CuO4 and Nd2-x Ce x CuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2-x Ce x CuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates.
理解电荷有序（CO）与其他现象（例如赝能隙、反铁磁和超导）之间的相互作用是铜酸盐高温超导体的核心问题之一。在空穴和电子掺杂铜酸盐中都存在相似形式的 CO 的发现为确定 CO 现象学的哪一部分对所有铜酸盐都是普遍存在的开辟了一条道路。我们使用共振 X 射线散射来测量电子掺杂铜酸盐（La2-xCexCuO4 和 Nd2-xCexCuO4）中的 CO 相关性及其与反铁磁、赝能隙和超导的关系。对 Nd2-xCexCuO4 的详细测量表明，CO 存在于 x = 0.059 到 0.166 范围内，其掺杂依赖性波矢与费米面直段之间的间隔一致。CO 的起始温度在 x = 0.106 到 0.166 之间最高，但在较低的掺杂水平下降低，表明它与反铁磁相关性或赝能隙的出现无关。在近最佳掺杂下，CO 波矢也与先前观察到的声子异常一致，在超导转变温度以下和以上或在磁场中测量 CO 表明 CO 对超导性不敏感。总的来说，这些发现表明，尽管在电子掺杂铜酸盐中得到了验证，但材料依赖性细节决定了 CO 相关性是否获得足够的强度来争夺铜酸盐的基态。
