[论文解读] Theoretical analysis on the possibility of superconductivity in a trilayer Ruddlesden-Popper nickelate La$_4$Ni$_3$O$_{10}$ under pressure and its experimental examination: comparison with La$_3$Ni$_2$O$_7$

Hirofumi Sakakibara, Masayuki Ochi+10 more|arXiv (Cornell University)|Sep 18, 2023

Magnetic and transport properties of perovskites and related materials参考文献 92被引用 11

一句话总结

该论文用基于DFT的模型结合FLEX与Eliashberg形式来理论分析La4Ni3O10在高压下是否可能成为超导体，并辅以对相关镍氧化物在高压下的传输实验以与La3Ni2O7进行比较。

ABSTRACT

We study the possibility of superconductivity in a trilayer Ruddlesden-Popper nickelate La$_4$Ni$_3$O$_{10}$ under pressure both theoretically and experimentally, making comparison with the recently discovered high $T_c$ superconductor La$_3$Ni$_2$O$_7$, a bilayer nickelate. Through DFT calculations, we find that a structural phase transition from monoclinic to tetragonal takes place around 10 - 15 GPa. Using the tetragonal crystal structure, we theoretically investigate the possibility of superconductivity, where a combination of fluctuation exchange approximation and linearized Eliashberg equation is applied to a six-orbital model constructed from first principles band calculation. The obtained results suggests that La$_4$Ni$_3$O$_{10}$ may also become superconducting under high pressure with $T_c$ comparable to some cuprates, although it is not as high as La$_3$Ni$_2$O$_7$. We also perform experimental studies using our polycrystalline samples of La$_3$Ni$_2$O$_{7.01}$ and La$_4$Ni$_3$O$_{9.99}$. The superconducting transition of La$_3$Ni$_2$O$_{7.01}$, with a maximum onset $T_c$ of 67.0 K at a pressure of 26.5 GPa, is confirmed by a drop in the electrical resistance, as well as the magnetic field dependence of the resistance. Quite interestingly, similar temperature and magnetic field dependencies of the resistance are observed also for La$_4$Ni$_3$O$_{9.99}$, where a drop in the resistance is observed at lower temperatures compared to La$_3$Ni$_2$O$_{7.01}$, under pressures of 32.8 GPa and above. Given the theoretical expectation, the reduction in the resistance can most likely be attributed to the occurrence of superconductivity in La$_4$Ni$_3$O$_{9.99}$. The temperature at which the resistance deviates from a linear behavior, considered as the onset $T_c$, monotonically increases up to 23 K at 79.2 GPa, which is opposite to the pressure dependence of $T_c$ in La3Ni2O7.01.

研究动机与目标

• 在高压下推动对三层镍酸镍氧化物在超导性中的潜在探索，并理解维度与轨道物理如何影响成对机制。
• 在高压下为La4Ni3O10建立基于第一性原理的六轨道模型，并通过自旋涨落介导的成对来评估超导性。
• 将理论预期与La3Ni2O7.12以及La4Ni3O9.99在高压下的电阻测量进行比较，以识别超导性的标志。
• 研究在压力下的结构相变，并将四方相确认为潜在超导性相关的工作区间。

提出的方法

• 在VASP中使用PBEsol和PAW执行DFT计算以在压力下优化结构。
• 在约20 GPa处识别单斜到四方的转变，并通过声子计算验证四方相（无虚模）。
• 基于40 GPa的四方结构，使用Wannier90构建一个六轨道（三层Ni×两个Ni轨道）的紧束缚模型。
• 应用带上作用点相互作用（U、U'、J、J'）的FLEX并解线性化Eliashberg方程以获得超导特征值λ，作为Tc的代理。
• 分析在成键、反键和非成键的d3z2−r2带中的超导能隙函数及其掺杂依赖性。
• 将La4Ni3O10的理论发现与先前研究的La3Ni2O7进行比较，以评估相对Tc的预期。

实验结果

研究问题

• RQ1 在其四方相中，La4Ni3O10能在高压下成为超导体吗？
• RQ2 La4Ni3O10中类Fe自旋涨落和多轨道带如何影响与La3Ni2O7相比的超导成对？
• RQ3 带填充和存在非成键的d3z^2−r^2带对超导特征值λ有何影响？
• RQ4 相关镍酸盐在高压下的电阻行为的实验观测是否与超导解释一致？

主要发现

层间差异	ΔE（eV）	t_perp（eV）	t_{3z^2−r^2}（eV）	t_{x^2−y^2}（eV）	t_{x^2−y^2−3z^2−r^2}（eV）
inner	0.105	-0.712	-0.163	-0.541	-0.294
outer	0.257	-0.117	-0.538	-0.285	-0.000
La3Ni2O7	0.372	-0.664	-0.117	-0.491	-0.242

• DFT预测在约20 GPa处出现单斜到四方转变，在更高压力下稳定的四方结构I4/mmm。
• 在40 GPa下的La4Ni3O10的六轨道模型给出一个超导特征值λ，相对于La3Ni2O7有所下降但仍然相当（大致在一些銅氧化物中观测到的范围内）。
• La4Ni3O10的λ在接近计量比时局部达到最大，因为在该区域所有三个d3z^2−r^2带都对超导性有贡献。
• 超导能隙函数分析显示在成键/反键和非成键带之间存在符号变化，表明存在多带层间成对的倾向。
• 实验观测中，La3Ni2O7.12在26.1 GPa时Tc起始约78 K，而La4Ni3O9.99在更高压力下出现电阻下降，起始温度上升至约23 K在79.2 GPa，提示在受压下三层样品可能存在超导性。