Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea.
Department of Applied Mathematics and Physics, Tottori University, Tottori 680-8552, Japan.
Sci Rep. 2016 Sep 16;6:33397. doi: 10.1038/srep33397.
Many important questions for high-Tc cuprates are closely related to the insulating nature of parent compounds. While there has been intensive discussion on this issue, all arguments rely strongly on, or are closely related to, the correlation strength of the materials. Clear understanding has been seriously hampered by the absence of a direct measure of this interaction, traditionally denoted by U. Here, we report a first-principles estimation of U for several different types of cuprates. The U values clearly increase as a function of the inverse bond distance between apical oxygen and copper. Our results show that the electron-doped cuprates are less correlated than their hole-doped counterparts, which supports the Slater picture rather than the Mott picture. Further, the U values significantly vary even among the hole-doped families. The correlation strengths of the Hg-cuprates are noticeably weaker than that of La2CuO4. Our results suggest that the strong correlation enough to induce Mott gap may not be a prerequisite for the high-Tc superconductivity.
许多关于高温超导铜酸盐的重要问题都与母体化合物的绝缘性质密切相关。虽然对此问题已经进行了深入的讨论，但所有的论点都强烈依赖于或与材料的关联强度密切相关。由于缺乏对这种相互作用的直接测量（传统上用 U 表示），因此严重阻碍了对此问题的清晰理解。在这里，我们报告了几种不同类型的铜酸盐的 U 的第一性原理估计。U 值随顶角氧与铜之间的反键距离的倒数而明显增加。我们的结果表明，电子掺杂的铜酸盐比空穴掺杂的铜酸盐的相关性更小，这支持斯莱特图像而不是莫特图像。此外，即使在空穴掺杂的家族中，U 值也有很大的差异。Hg-铜酸盐的关联强度明显弱于 La2CuO4。我们的结果表明，足以诱导莫特能隙的强关联可能不是高温超导性的先决条件。
