标题： Ruddlesden-Popper镍酸盐$m$层状超导体La$_{m+1}$Ni$_{m}$O$_{3m+1}$ 的电子结构、超导配对以及磁相关的一般趋势 显示英文标题

标题： General trends of electronic structures, superconducting pairing, and magnetic correlations in the Ruddlesden-Popper nickelate $m$-layered superconductors La$_{m+1}$Ni$_{m}$O$_{3m+1}$

摘要： 我们报道了对加压下Ruddlesden-Popper层状镍酸盐La$_{m+1}$Ni$_m$O$_{3m+1}$ ($m = 1$至6)的全面理论分析。我们的结果显示，尽管这些Ruddlesden-Popper层状镍酸盐有许多相似之处，但也显示出明显的差异。Ni$d_{3z^2-r^2}$轨道根据堆叠层数$m$的奇偶性，表现出成键-反成键、成键-反成键-非成键的特征分裂。 此外，在La$_{m+1}$Ni$_m$O$_{3m+1}$ ($m = 1$至6)中发现，$d_{3z^2-r^2}$和$d_{x^2-y^2}$轨道之间的面内轨道间跃迁与$d_{x^2-y^2}$轨道之间的面内轨道内跃迁的比率较大，并且该比率从$m = 1$增加到$m = 6$，表明随着层数$m$的增加，面内杂化将会增强。 与双层 La$_3$Ni$_2$O$_7$和三层 La$_4$Ni$_3$O$_{10}$中由自旋涨落驱动的主导$s^\pm$波态相反，在四层堆叠 La$_5$Ni$_4$O$_{13}$和五层堆叠 La$_6$Ni$_5$O$_{16}$中获得了两个几乎简并的$d_{x^2-y^2}$波和$s^\pm$波主导态。 在六层材料La$_7$Ni$_6$O$_{19}$中恢复了主要的$s^\pm$波态。 一般来说，在随机相位近似处理的层面上，对于化学计量比的块体系统，尽管存在$m$依赖的主导配对，超导转变温度$T_c$从双层 La$_3$Ni$_2$O$_7$降低到六层 La$_7$Ni$_6$O$_{19}$。 发现面内和面外磁性关联都相当复杂。 在面内方向上，我们在 La$_5$Ni$_4$O$_{13}$和 La$_7$Ni$_6$O$_{19}$中获得了磁化率峰${\bf q} = (0.6 \pi, 0.6 \pi)$，在 La$_6$Ni$_5$O$_{16}$中获得了磁化率峰${\bf q} = (0.7 \pi, 0.7 \pi)$。 显示英文摘要

摘要： We report a comprehensive theoretical analysis of the Ruddlesden-Popper layered nickelates La$_{m+1}$Ni$_m$O$_{3m+1}$ ($m = 1$ to 6) under pressure. Our results suggest that, while these Ruddlesden-Popper layered nickelates display many similarities, they also show noticeable differences. The Ni $d_{3z^2-r^2}$ orbitals display bonding-antibonding, or bonding-antibonding-nonbonding, characteristic splittings, depending on the even or odd number of stacking layers $m$. In addition, the ratio of the in-plane interorbital hopping between $d_{3z^2-r^2}$ and $d_{x^2-y^2}$ orbitals and in-plane intraorbital hopping between $d_{x^2-y^2}$ orbitals was found to be large in La$_{m+1}$Ni$_m$O$_{3m+1}$ ($m = 1$ to 6), and this ratio increases from $m = 1$ to $m = 6$, suggesting that the in-plane hybridization will increase as the layer number $m$ increases. In contrast to the dominant $s^\pm$--wave state driven by spin fluctuations in the bilayer La$_3$Ni$_2$O$_7$ and trilayer La$_4$Ni$_3$O$_{10}$, two nearly degenerate $d_{x^2-y^2}$-wave and $s^\pm$-wave leading states were obtained in the four-layer stacking La$_5$Ni$_4$O$_{13}$ and five-layer stacking La$_6$Ni$_5$O$_{16}$. The leading $s^\pm$-wave state was recovered in the six-layer material La$_7$Ni$_6$O$_{19}$. In general, at the level of the random phase approximation treatment, the superconducting transition temperature $T_c$ decreases in stoichiometric bulk systems from the bilayer La$_3$Ni$_2$O$_7$ to the six-layer La$_7$Ni$_6$O$_{19}$, despite the $m$ dependent dominant pairing. Both in-plane and out-of-plane magnetic correlations are found to be quite complex. Within the in-plane direction, we obtained the peak of the magnetic susceptibility at ${\bf q} = (0.6 \pi, 0.6 \pi)$ for La$_5$Ni$_4$O$_{13}$ and La$_7$Ni$_6$O$_{19}$, and at ${\bf q} = (0.7 \pi, 0.7 \pi)$ for La$_6$Ni$_5$O$_{16}$.