发表机构
Center for High Pressure Science and Technology Advanced Research; Renmin University of China; Institute of Physics, Chinese Academy of Sciences; University of Chinese Academy of Sciences（高压力科学与技术前沿研究中心; 中国人民大学; 中国科学院物理研究所; 中国科学院大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合第一性原理计算、两轨道模型与自洽FLEX方法，揭示了无限层La$_{0.8}$Sr$_{0.2}$NiO$_2$中超导穹顶及兆巴压力下稳定性的微观起源，阐明了压力调控配对的机制。
AI 中文摘要
近期对自支撑La$_{0.8}$Sr$_{0.2}$NiO$_2$薄膜的输运测量发现，其存在一个从常压延伸至210 GPa的宽超导穹顶，在146 GPa附近起始转变温度可达74.5 K。我们结合第一性原理计算、压力相关的两轨道模型，以及与线性化Eliashberg方程结合的自洽FLEX计算，明确了压力压缩如何改变配对趋势。压力会提升动能标度、降低$U_x/t_1$、增强层间杂化，并将空穴从La/Sr衍生的电荷库转移至关联Ni区域。在当前低能描述下，动能标度的提升与体系向最优中间耦合的趋近是配对初始增强的原因，而压力诱导的自掺杂进入过掺杂区则是高压下超导被抑制的主要原因。尽管费米面出现显著的三维化，与配对相关的自旋磁化率对$q_z$的依赖仍然较弱，且在$(π,π)$附近达到峰值。因此，以Ni-$d_{x^2-y^2}$为主的$d$波配对态在计算的压力范围内保持稳定。这些结果为超导穹顶及其在兆巴压力下的异常稳定性提供了统一的微观解释。
英文摘要
Recent transport measurements on freestanding La$_{0.8}$Sr$_{0.2}$NiO$_2$ membranes revealed a broad superconducting dome extending from ambient pressure to 210 GPa, with an onset transition temperature reaching 74.5 K near 146 GPa. Using first-principles calculations, a pressure-dependent two-orbital model, and self-consistent FLEX calculations combined with the linearized Eliashberg equation, we determine how compression modifies the pairing tendency. Pressure increases the kinetic-energy scale, reduces $U_x/t_1$, strengthens interlayer hybridization, and transfers holes from the La/Sr-derived charge reservoir to the correlated Ni sector. Within the present low-energy description, the increasing kinetic scale and the approach to optimal intermediate coupling account for the initial enhancement of pairing, whereas pressure-induced self-doping into the overdoped regime is primarily responsible for its high-pressure suppression. Despite a pronounced three-dimensionalization of the Fermi surface, the pairing-relevant spin susceptibility remains weakly dependent on $q_z$ and peaked near $(π,π)$. Consequently, the Ni-$d_{x^2-y^2}$-dominated $d$-wave pairing state remains stable over the calculated pressure range. These results provide a unified microscopic interpretation of both the superconducting dome and its unusual robustness under megabar compression.
Comments6 pages, 3 figures
