发表机构
Sun Yat-sen University（中山大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过DFT和RPA计算系统研究了四层RP镍酸盐La$_5$Ni$_4$O$_{13}$在环境压力和不同应变下的电子结构，构建了双轨道模型，并发现c轴压缩可增强自旋涨落，为超导电性提供有利条件。
AI 中文摘要
Ruddlesden-Popper（RP）镍酸盐中压力诱导超导电性的发现激发了对高T$_c$超导体的广泛兴趣。在此，我们利用密度泛函理论（DFT）和随机相位近似（RPA）计算，系统研究了四层RP镍酸盐La$_5$Ni$_4$O$_{13}$在环境压力、5%各向同性压缩应变和4% c轴单轴应变下的电子性质。DFT计算表明，各向同性应变拓宽了Ni-$e_g$能带并诱导了从O-$p$到Ni-$d$轨道的电荷转移，而c轴单轴应变则选择性地将$d_{z^2}$衍生的bonding1能带上移，同时几乎不改变$d_{x^2-y^2}$的色散。通过Wannier降维，我们构建了一个四层双轨道模型，该模型重现了低能Ni-$e_g$能带。我们的模型揭示，在环境压力和5%各向同性应变下，费米面由两个电子口袋（$\alpha$和$\delta$）和三个空穴口袋（$\beta$、$\beta^{\prime}$和$\beta^{\prime \prime}$）组成，而在单轴应变下，出现了一个具有$d_{z^2}$轨道特征的$\gamma$空穴口袋。RPA计算表明，主导的自旋响应从环境压力下的$\mathbf{q}\approx(2\pi/3,2\pi/3)$转变为两种应变条件下的$\mathbf{q}\approx(\pi,\pi)$，并在c轴压缩下得到增强。这些结果表明，c轴压缩可能为四层镍酸盐中的超导电性提供一条有利途径，类似于双层和三层镍酸盐中的情况。
英文摘要
The discovery of pressure-induced superconductivity in Ruddlesden--Popper (RP) nickelates has stimulated extensive interest in high-T$_c$ superconductors. Here, we systematically study the electronic properties of the quadlayer RP nickelate La$_5$Ni$_4$O$_{13}$ under ambient pressure, 5% isotropic compressive strain, and 4% $c$-axis uniaxial strain using density functional theory (DFT) and random phase approximation (RPA) calculations. DFT calculations show that isotropic strain broadens the Ni-$e_g$ bands and induces charge transfer from O-$p$ to Ni-$d$ orbitals, whereas $c$-axis uniaxial strain selectively shifts the $d_{z^2}$-derived bonding1 band upward while leaving the $d_{x^2-y^2}$ dispersion nearly unchanged. From Wannier downfolding, we construct a quadlayer two-orbital model that reproduces the low-energy Ni-$e_g$ bands. Our model reveals that under ambient pressure and 5% isotropic strain, the Fermi surface consists of two electron pockets ($α$ and $δ$) and three hole pockets ($β$, $β^{\prime}$, and $β^{\prime \prime}$), while under uniaxial strain, a $γ$ hole pocket with $d_{z^2}$ orbital character emerges. RPA calculations reveal that the leading spin response shifts from $\mathbf{q}\approx(2π/3,2π/3)$ at ambient pressure to $\mathbf{q}\approx(π,π)$ under both strain conditions and is enhanced under $c$-axis compression. These results suggest that $c$-axis compression may provide a favorable route to superconductivity in the quadlayer nickelate analogous to that in bilayer and trilayer nickelates.
