John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2018 Oct 12;121(15):157001. doi: 10.1103/PhysRevLett.121.157001.
For copper-based superconductors, the maximum superconducting transition temperature T_{c,max} of different families measured from experiment can vary from 38 K in La_{2}CuO_{4} to 135 K in HgBa_{2}Ca_{2}Cu_{3}O_{8} at the optimal hole doping concentration. We demonstrate herein, using ab initio computations, a new trend suggesting that the cuprates with stronger out-of-CuO_{2}-plane chemical bonding between the apical anion (O, Cl) and apical cation (e.g., La, Hg, Bi, Tl) are generally correlated with higher T_{c,max} in experiments. We then show the underlying fundamental phenomena of coupled apical charge flux and lattice dynamics when the apical oxygen oscillates vertically. This triggers the charge flux among the apical cation, apical anion, and the in-plane CuO_{4} unit. The effect not only dynamically modulates the site energy of the hole at a given Cu site to control the in-plane charge transfer energy, but also can modulate the in-plane hole hopping integral simultaneously in a dynamic way by the cooperative apical charge fluxes.
对于铜基超导体，从实验中测量的不同家族的最大超导转变温度 T_{c,max}在最佳空穴掺杂浓度下可以从 La_{2}CuO_{4}的 38 K 变化到 HgBa_{2}Ca_{2}Cu_{3}O_{8}的 135 K。本文通过第一性原理计算证明了一个新的趋势，即在 CuO_{2}-平面之外，顶点阴离子（O、Cl）和顶点阳离子（如 La、Hg、Bi、Tl）之间的化学结合越强的铜酸盐通常与实验中更高的 T_{c,max}相关。然后，我们展示了当顶点氧垂直振荡时，耦合的顶点电荷流和晶格动力学的基本现象。这会引发在顶点阳离子、顶点阴离子和平面 CuO_{4}单元之间的电荷流。该效应不仅动态地调节了给定 Cu 位上的空穴的位能以控制平面内的电荷转移能，而且还可以通过协同的顶点电荷流以动态方式同时调制平面内的空穴跃迁积分。
