Contrasting Spin Excitations in Octahedral and Square-Planar n=8 Ruddlesden-Popper Nickelates
Yale University（耶鲁大学）；Flatiron Institute（平顿研究所）；Harvard University（哈佛大学）；Donostia International Physics Center (DIPC)（多诺斯蒂亚国际物理中心）；University of California San Diego（加利福尼亚大学圣迭戈分校）；European Synchrotron Radiation Facility（欧洲同步辐射装置）
K. Scott, H. LaBollita, G. A. Pan, X. Yang, A. Kar, C. Lim, A. Thorshov, D. Ferenc Segedin, C. M. Brooks, F. Yakhou-Harris, K. Kummer, N. B. Brookes, F. Boschin… 展开作者
K. Scott, H. LaBollita, G. A. Pan, X. Yang, A. Kar, C. Lim, A. Thorshov, D. Ferenc Segedin, C. M. Brooks, F. Yakhou-Harris, K. Kummer, N. B. Brookes, F. Boschini, A. Frano, J. A. Mundy, E. H. da Silva Neto, A. S Botana, S. Blanco-Canosa
The discovery of superconductivity in reduced square-planar nickelates marked a major advance in identifying structural and electronic analogs to the high-$T_c$ cuprates. The more recent observation of superconductivity in parent Ruddlesden-Popper (RP) octahedral nickelates with a clear difference in electron count with respect to cuprates raises new questions about the nature of superconductivity across these related but distinct nickelate families. Here, we use Ni $L_3$-edge resonant inelastic x-ray scattering (RIXS) to probe the low-energy excitations in a representative compound of both families: the parent octahedral $n=8$ RP phase Nd$_9$Ni$_8$O$_{25}$ (p-RP), which is non-superconducting, and its reduced square-planar counterpart Nd$_9$Ni$_8$O$_{18}$ (r-RP), which exhibits superconducting correlations with a $T_c \approx 5$ K. The $n=8$ p-RP develops a spin-density-wave (SDW) ground state with ordering wave vector $q_{\mathrm{SDW}} = (1/4,\, 1/4)$, analogous to the bilayer RP, while the $n=8$ r-RP shows an elastic peak at $q^\star = (1/3,\, 0)$. Polarimetric RIXS shows that the p-RP exhibits low-energy spectra dominated by weakly dispersive paramagnons along the 0$\rightarrowπ$ and $π\!\rightarrow\! π$ directions, whereas the r-RP with superconducting correlations displays dispersionless magnetic excitations. Our results comprehensively map out the spin excitations and reveal fundamental differences in the ground state between these two distinct structural families.
Resonant inelastic x-ray scattering data for Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates
Ruddlesden-Popper和还原Ruddlesden-Popper镍酸盐是模拟高温超导铜酸盐性质的有趣候选者。这些镍酸盐和铜酸盐之间的相似程度一直是相当大的辩论的主题。共振非弹性X射线散射（RIXS）在探索它们的电子和磁激发方面发挥了重要作用，但这些努力因不同样品之间的不一致性和缺乏公开可用的数据进行详细比较而受到阻碍。为了解决这个问题，我们提出了开放RIXS数据La 4 Ni 3 O 10和La 4 Ni 3 O 8。
Epitaxial growth of Ruddlesden-Popper neodymium nickelates Nd$_{n+1}$Ni$_{n}$O$_{3n+1}$ (${n}$ = 1-5)
采用反应分子束外延技术制备了一系列Ruddlesden-Popper镍酸盐（Nd $_{n+1}$ Ni $_{n}$ O $_{3n+1}$（${n}$ = 1-5））的稳定薄膜。X射线衍射和扫描透射电子显微镜证实了高结晶质量。X射线光电子能谱学表明这些化合物中镍的${n}$依赖价态。金属-绝缘体转变显示出明显的${n}$依赖于中间成员（${n}$ = 3-5），其低温电阻率显示对数依赖性，类似于在超导无限层镍酸盐的母体化合物中观察到的Kondo散射。
Electronic structure of higher-order Ruddlesden-Popper nickelates
我们用第一性原理计算分析了最近合成的高阶镍酸盐Ruddlesden-Popper相La $_{n+1}$ Ni $_n$ O $_{3n+1}$（$n=4-6$）的电子结构.对于所有的材料，我们的研究结果表明，大的孔状费米表面与$d_{x^2-y^2}$字符，非常类似的最佳空穴掺杂的铜酸盐。对于较高的$n$值，额外的非铜酸盐样带的$d_{z^2}$轨道特征出现。这些方面突出表明，该Ruddlesden-Popper系列可以提供一种通过调节镍酸盐的维度来修改其电子基态的手段。由于它们与铜酸盐的相似性和差异性，这种新的材料家族可能会揭示铜基氧化物的物理学。
Interlayer electronic coherence links magnetism and superconductivity in Ruddlesden-Popper nickelates
State Key Laboratory of Surface Physics and Department of Physics, Fudan University（复旦大学表面物理国家重点实验室和物理系）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Institute of Nanoelectronics and Quantum Computing, Fudan University（复旦大学纳米电子与量子计算研究所）
Comparative Raman study of Ruddlesden-Popper nickelates and the monolayer-trilayer polymorph
Max-Planck-Institute for Solid State Research（马克斯·普朗克固体的研究所）；Hefei National Laboratory（合肥国家实验室）；University of Science and Technology Beijing（北京科技大学）；University of Stuttgart（斯图加特大学）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）
Three-Dimensional Electronic Structures in Superconducting Ruddlesden-Popper Bilayer Nickelate Films
Southern University of Science and Technology（南方科技大学）；Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area（粤港澳大湾区量子科学中心）；University of Science and Technology of China（中国科学技术大学）；Shanghai Jiao Tong University（上海交通大学）；Tsinghua University（清华大学）
Magnetism in artificial Ruddlesden-Popper iridates leveraged by structural distortions
我们报道了由单层和双层SrIrO $_3$与SrTiO $_3$间隔组成的超晶格中磁相互作用的调谐。磁散射显示占主导地位的$c$轴反铁磁取向的磁矩的双层证明这些系统作为可行的人工类似物的散装Ruddlesden-Popper系列铱酸盐。在两种超晶格中均观察到磁振子能隙，双层中的能隙大小减小到其体结构类似物Sr $_3$ Ir $_2$ O $_7$的近一半。我们将此分配给修改的各向异性交换驱动的弯曲的$c$轴Ir-O-Ir键和随后的局部环境的变化，通过X射线衍射检测和使用自旋波理论建模。这些发现解释了即使是由虹膜状结构中的异质结构驱动的细微结构调制，也是如何通过自旋轨道耦合来驱动磁相互作用的巨大变化的。
Dissecting superconductivity in the Ruddlesden-Popper nickelates: The role of electron correlation and interlayer magnetic exchange
Diamond Light Source（钻石光源）；National Synchrotron Radiation Laboratory and School of Nuclear Science and Technology, University of Science and Technology of China（中国科学技术大学核科学与技术学院/国家同步辐射实验室）；Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University（中山大学物理学院/广东省铁电与磁器件重点实验室）；Department of Physics, University of Oxford（牛津大学物理系）；National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University（南京大学固体微结构物理国家重点实验室/物理学院）；Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学先进微结构协同创新中心）
Itinerant Nature of Spin-Density-Wave Order in Ruddlesden-Popper Nickelates
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）
Thermodynamic phase transition, pairing symmetry and Fermi surface topology in Ruddlesden-Popper nickelate films
University of Science and Technology of China（中国科学技术大学）；Hefei National Laboratory, University of Science and Technology of China（合肥国家实验室，中国科学技术大学）；Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China（中国科学院微观结构国家重点实验室，中国科学技术大学）
Relativistic $GW$+BSE study of the optical properties of Ruddlesden-Popper iridates
通过求解Bethe-Salpeter方程（BSE）研究了Ruddlesden-Popper系列铱酸盐Sr $_{n+1}$ Ir $_n$ O $_{3n+1}$（$n$ =1，2和$\infty$）的光学性质，其中准粒子（QP）能量和屏蔽相互作用$W$由包含自旋轨道耦合的$GW$近似得到.计算的光学电导率谱显示出很强的激子效应，并很好地再现了实验观察到的双峰结构，特别是自旋轨道莫特绝缘体Sr $_2$ IrO $_4$和Sr $_3$ Ir $_2$ O $_7$。然而，$GW$不能很好地解释SrIrO $_3$的相关金属态，这是由于太小的能带重整化，这影响了光学电导率的整体质量。我们的分析很好地描述了作为维数（$n$）的函数的主要光学峰的渐进红移，这与电子相关性（由约束随机相位近似量化）向金属$n=\infty$极限的逐渐降低相关。我们还评估了一种计算成本更低的BSE方法的质量，该方法基于模型介电函数并在DFT+ $U$单电子能量之上进行。不幸的是，该模型BSE方法不能准确地再现完整的$GW$ +BSE方法的结果，并导致测量光谱的较大偏差。
Electronic structures across superconductor-insulator transition in Ruddlesden-Popper bilayer nickelate films
University of Science and Technology of China（中国科学技术大学）；Hefei National Laboratory, University of Science and Technology of China（合肥国家实验室，中国科学技术大学）；Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China（微观尺度物理科学合肥国家研究中心，中国科学技术大学）；Southern University of Science and Technology（南方科技大学）；Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area（粤港澳大湾区量子科学中心）；Nanjing University（南京大学）；Shanghai Jiao Tong University（上海交通大学）；Tsinghua University（清华大学）
Enhancement of giant magnetoresistance effect in the Ruddlesden-Popper phase Sr3Fe2-xCoxO7-d: Predominant role of oxygen nonstoichiometry and magnetic phase separation
General trends of electronic structures, superconducting pairing, and magnetic correlations in the Ruddlesden-Popper nickelate $m$-layered superconductors La$_{m+1}$Ni$_{m}$O$_{3m+1}$
University of Tennessee（田纳西大学）；Oak Ridge National Laboratory（橡树岭国家实验室）
Layer Architecture Shapes Electronic, Magnetic, and Lattice Interactions in Ruddlesden-Popper Nickelates
Brookhaven National Laboratory（布鲁克海文国家实验室）；Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory（斯坦福物质与能源科学研究所，SLAC国家加速器实验室）；The University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校）；Harvard University（哈佛大学）；Argonne National Laboratory（阿贡国家实验室）；Oak Ridge National Laboratory（橡树岭国家实验室）；National Synchrotron Light Source II, Brookhaven National Laboratory（国家同步光源二期，布鲁克海文国家实验室）
Distinguishing Electronic Band Structure of Single-layer and Bilayer Ruddlesden-Popper Nickelates Probed by in-situ High Pressure X-ray Absorption Near-edge Spectroscopy
Electronic Origin of Density Wave Orders in a Trilayer Nickelate
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University（中山大学物理学院广东省磁电物理与器件重点实验室）；Technical Institute of Physics and Chemistry, Chinese Academy of Sciences（中国科学院化学物理研究所）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）
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$_7$
Electronic structure, magnetic correlations, and superconducting pairing in the reduced Ruddlesden-Popper bilayer La$_3$Ni$_2$O$_6$ under pressure: different role of $d_{3z^2-r^2}$ orbital compared with La$_3$Ni$_2$O$_7$
Spin-density-wave transition in monolayer-trilayer La3Ni2O7 single crystals
ShanghaiTech University（上海科技大学）；Songshan Lake Materials Laboratory（松山湖材料实验室）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Beijing National Laboratory for Condensed Matter Physics（北京凝聚态物理国家研究中心）；University of Chinese Academy of Sciences（中国科学院大学）；Center for High Pressure Science and Technology Advanced Research（高压科学先进研究发展中心）；Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments (MFree)（极端环境材料前沿研究上海市重点实验室）；Institute for Shanghai Advanced Research in Physical Sciences (SHARPS)（上海高等研究院物理科学研究所）；ShanghaiTech Laboratory for Topological Physics（上海科技大学拓扑物理实验室）；Shanghai Key Laboratory of High-resolution Electron Microscopy（高分辨电子显微学上海市重点实验室）；Department of Physics, Clarendon Laboratory, University of Oxford（牛津大学克拉伦登实验室物理系）；School of Physical Sciences, Great Bay University（大湾区大学物理科学学院）
Nearly perfect Fermi surface nesting in hole-doped La$_3$Ni$_2$O$_7$ enables bulk superconductivity without pressure or strain
NYU-ECNU Institute of Physics, NYU Shanghai（纽约大学-华东师范大学物理研究所，上海纽约大学）；Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University（华东师范大学极化材料与器件教育部重点实验室）；Department of Physics, Brown University（布朗大学物理系）；Department of Physics, New York University（纽约大学物理系）
Bandwidth-Controlled Insulator-Metal Transition and Correlated Metallic State in 5$d$ Transition Metal Oxides Sr$_{n+1}$Ir$_{n}$O$_{3n+1}$ ($n$=1, 2, and $\infty$)
我们利用光谱学和第一性原理计算研究了5 $d$ Ruddlesden-Popper系列Sr $_{n+1}$ Ir $_{n}$ O $_{3n+1}$（$n$ =1，2和$\infty$）的电子结构.由于5个$d$轨道在空间上比3个$d$或4个$d$轨道延伸得更远，因此人们普遍认为5个$d$化合物中的相关效应最小。然而，当我们增加$n$时，我们观察到从Mott绝缘体到金属的带宽控制过渡。此外，人工合成的钙钛矿SrIrO $_{3}$显示出约6的非常大的质量增强，表明其处于相关金属状态。
Spectroscopic evidence for polaronic behaviour of the strong spin-orbit insulator Sr$_3$Ir$_2$O$_7$
本文利用温度依赖角分辨光电子能谱研究了双层Ruddlesden-Popper铱酸盐Sr $_3$ Ir $_2$ O $_7$。我们发现一个窄间隙相关绝缘体，与极化基态的光谱特征指示，惊人的相似，以前观察到的铜酸盐超导体的母体化合物。我们还观察到类似的行为为单层表弟Sr $_2$ IrO $_4$，表明强电子-玻色子耦合占主导地位的低能量激发这种异国情调的家庭的材料，并提供了一个微观之间的联系绝缘基态的完全不同的3D铜酸盐和5D铱酸盐。
