标题： 基于Bethe-Salpeter方程方法的CDW临界点附近超导性和质量增强理论：应用于铜氧化物高温超导体 显示英文标题

标题： Theory of superconductivity and mass enhancement near CDW critical point based on Bethe-Salpeter equation method: application to cuprates

摘要： 近年来，强关联金属中的电荷通道序引起了广泛关注。著名的例子是铜氧化物和铁基超导体中的电子向列序，以及kagome金属中的大卫之星序。由这些电荷通道序涨落产生的临界现象和非常规超conductivity 是当前的核心问题；然而，顶点修正在其中起着关键作用，这些是传统平均场类型近似中被忽略的多体效应。为了解决这一困难，在本研究中，我们提出了Bethe-Salpeter方程理论来评估二维Hubbard模型中的电子-电子相互作用。该方法满足Baym-Kadanoff保守近似的标准。在这里，我们发现电荷通道中出现了一种吸引相互作用，这是描述自旋涨落之间干涉过程的Aslamazov-Larkin顶点修正的结果。将此方法应用于平方晶格Hubbard模型，我们揭示了吸引电荷涨落和排斥自旋涨落的协同作用共同导致了高-$T_c$ $d$ -波超conductivity 以及增强的有效质量。这些结果自然解释了铜氧化物超conductors的相图，在此处强耦合$d$-波超conductivity 出现在电荷序量子临界点附近。该理论也可以应用于多轨道Hubbard模型，如铁基和镍酸盐超conductors，表明未来应用的广阔潜力。 显示英文摘要

摘要： In recent years, charge-channel orders in strongly correlated metals have attracted great attention. Famous examples are the electronic nematic orders in cuprates and iron-based superconductors, and Star-of-David order in kagome metals. Critical phenomena and unconventional superconductivity arising from fluctuations of such charge-channel orders are central issues today; however, the essential role is played by the vertex corrections, which are the many-body effects that are dropped in conventional mean-field type approximations. To solve this difficulty, in this study, we propose the Bethe-Salpeter equation theory to evaluate electron-electron interactions in two dimensional Hubbard models. This method satisfies the criteria of the Baym-Kadanoff conserving approximation. Here, we find that an attractive interaction in the charge channel emerges from the Aslamazov-Larkin vertex corrections that describe the interference processes among spin fluctuations. Applying this method to the square-lattice Hubbard model, we reveal that the cooperation of attractive charge fluctuations and repulsive spin fluctuations yields high-$T_c$ $d$-wave superconductivity together with enhanced effective mass. These results naturally explain the phase diagram of cuprate superconductors, where strong-coupling $d$-wave superconductivity appears near the charge-order quantum critical point. The theory can also be applied to multi-orbital Hubbard models, like iron-based and nickelate superconductors, suggesting broad potential for future applications.