Character of the "normal state" of the nickelate superconductors
Kyuho Lee, Bai Yang Wang, Motoki Osada, Berit H. Goodge, Tiffany C. Wang, Yonghun Lee, Shannon Harvey, Woo Jin Kim, Yijun Yu, Chaitanya Murthy, Srinivas Raghu, … 展开作者
Kyuho Lee, Bai Yang Wang, Motoki Osada, Berit H. Goodge, Tiffany C. Wang, Yonghun Lee, Shannon Harvey, Woo Jin Kim, Yijun Yu, Chaitanya Murthy, Srinivas Raghu, Lena F. Kourkoutis, Harold Y. Hwang
The occurrence of superconductivity in proximity to various strongly correlated phases of matter has drawn extensive focus on their normal state properties, to develop an understanding of the state from which superconductivity emerges. The recent finding of superconductivity in layered nickelates raises similar interests. However, transport measurements of doped infinite-layer nickelate thin films have been hampered by materials limitations of these metastable compounds - in particular, a relatively high density of extended defects. Here, by moving to a substrate (LaAlO$_{3}$)$_{0.3}$(Sr$_{2}$TaAlO$_{6}$)$_{0.7}$ which better stabilizes the growth and reduction conditions, we can synthesize the doping series of Nd$_{1-x}$Sr$_{x}$NiO$_{2}$ essentially free from extended defects. This enables the first examination of the 'intrinsic' temperature and doping dependent evolution of the transport properties. The normal state resistivity exhibits a low-temperature upturn in the underdoped regime, linear behavior near optimal doping, and quadratic temperature dependence for overdoping. This is strikingly similar to the copper oxides, despite key distinctions - namely the absence of an insulating parent compound, multiband electronic structure, and a Mott-Hubbard orbital alignment rather than the charge-transfer insulator of the copper oxides. These results suggest an underlying universality in the emergent electronic properties of both superconducting families.
Motivated by recent experimental studies on superconductivity found in nickelate-based materials, we study the temperature dependence of the spin correlation and the superconducting pairing interaction within an effective two-band Hubbard model by the quantum Monte Carlo method. Based on parameters extracted from first-principles calculations, our intensive numerical results reveal that the pairing with a $d_{xy}$-wave symmetry firmly dominates over other pairings at low temperature, which is mainly determined by the Ni 3$d$ orbital. It is also found that the effective pairing interaction is e…
Superconductor-insulator transitions in infinite-layer nickelates controlled via ${operando}$ monitored reduction
Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area（粤港澳大湾区量子科学中心）；State Key Laboratory of Quantum Functional Materials, Department of Physics, and Guangdong Basic Research Center of Excellence for Quantum Science, Southern University of Science and Technology（南方科技大学）；National Laboratory of Solid-State Microstructures, College of Engineering and Applied Sciences, Nanjing University（南京大学）；Department of Physics, City University of Hong Kong（香港城市大学）；Shenzhen Research Institute of City University of Hong Kong（香港城市大学（深圳）研究院）；Department of Physics, Tsinghua University（清华大学）
Bosonic phases across the superconductor-insulator transition in infinite-layer samarium nickelate
Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area（粤港澳大湾区量子科学中心）；Southern University of Science and Technology（南方科技大学）；City University of Hong Kong（香港城市大学）；Shenzhen Research Institute of City University of Hong Kong（香港城市大学深圳研究院）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Hefei National Laboratory（合肥国家实验室）；Peking University（北京大学）；Tsinghua University（清华大学）
Inspired by a recently proposed superconducting mechanism for a new cuprate superconductor Ba$_2$CuO$_{3+δ}$, we theoretically design an unconventional nickelate superconductor with $d^8$ electron configuration. Our strategy is to enlarge the on-site energy difference between $3d_{x^2-y^2}$ and other $3d$ orbitals by adopting halogens or hydrogen as out-of-plane anions, so that the $3d$ bands other than $d_{x^-y^2}$ lie just below the Fermi level for the $d^8$ configuration, acting as incipient bands that enhance superconductivity. We also discuss a possible relevance of the present proposal t…
Recent scanning tunneling microscopy (STM) observation of U-shaped and V-shaped spectra (and their mixture) in superconducting Nd$_{1-x}$Sr$_x$NiO$_2$ thin films has been interpreted as presence of two distinct gap symmetries in this nickelate superconductor [Gu et al., Nat. Comm. 11, 6027 (2020)]. Here, using a two-band model of nickelates capturing dominant contributions from Ni-$3d_{x^2-y^2}$ and rare-earth (R)-$5d_{3z^2 - r^2}$ orbitals, we show that the experimental observation can be simply explained within a pairing scenario characterized by a conventional $d_{x^2-y^2}$-wave gap structu…
Controlling the Band Filling and the Band Width in Nickelate Superconductors
RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所 emergent matter science 中心）；RIKEN Pioneering Research Institute（理化学研究所 先锋研究院）；The University of Tokyo（东京大学）；Department of Applied Physics, The University of Tokyo（东京大学 应用物理系）；Institute of Engineering Innovation, The University of Tokyo（东京大学 工程创新研究所）；Nanostructures Research Laboratory, Japan Fine Ceramics Center（日本精细陶瓷中心 纳米结构研究实验室）
Superconductivity has entered the nickel age marked by enormous experimental and theoretical efforts. Notwithstanding, synthesizing nickelate superconductors remains extremely challenging, not least due to incomplete oxygen reduction and topotactic hydrogen. Here, we present density-functional theory calculations, identify a phonon mode as a possible indication for topotactic hydrogen and discuss the charge redistribution patterns around oxygen and hydrogen impurities.
Motivated by the recent realization of the infinite-layer nickelate superconductivity (SC), we quantitatively investigate a two-orbital $d$-$s$ model by dynamic cluster quantum Monte Carlo calculations. Focusing on the impact of inter-orbital hybridization on the superconducting properties, our simulations indicate that the $d$-$s$ hybridization strength has a decisive role in the suppression of the $d$-wave pairing in the doping regime relevant to infinite-layer nickelates. Although we confirm on the single-orbital description at weak hybridization, at relatively large hybridization, there ex…
After the reward of more than two decades of pursuit on the high-Tc cuprate analog with the hope to obtain a better understanding of the mechanism of high-Tc superconductivity, the discovery of superconductivity in the infinite-layer nickelate brings more mystery to the picture than expected. Tops in the list of questions are perhaps (1) absence of superconductivity in the bulk nickelate and limited thickness of the infinite-layer phase in thin film, (2) absence of superconductivity in the La-nickelate despite it being the earliest studied rare-earth nickelate, and the role of 4f orbital in th…
The recently discovered infinite-layer nickelates show great promise in helping to disentangle the various cooperative mechanisms responsible for high-temperature superconductivity. However, lack of antiferromagnetic order in the pristine nickelates presents a challenge for connecting the physics of the cuprates and nickelates. Here, by using a quantum many-body Green's function-based approach to treat the electronic and magnetic structures, we unveil the presence of many two- and three-dimensional magnetic stripe instabilities that are shown to persist across the phase diagram of LaNiO$_2$. O…
Magnetism and superconductivity are closely entangled, elucidating the magnetic interactions in nickelate superconductors is at the heart of understanding the pairing mechanism. Our first-principles and spin-wave theory calculations highlight that NdNiO$_2$ is in the vicinity of a transition between a quasi-two-dimensional (2D) antiferromagnetic (AFM) state and a three-dimensional (3D) C-AFM state. Both states could accurately reproduce the experimentally measured magnetic excitation spectra, which was previously explained in terms of a 2D model. We further reveal that hole doping stabilizes a…
After decades of fundamental research, unconventional superconductivity has recently been demonstrated in rare-earth infinite-layer nickelates. The current view depicts these systems as a new category of superconducting materials, as they appear to be correlated metals with distinct multiband features in their phase diagram. Here, we provide an overview of the state of the art in this rapidly evolving topic.
Evolution of the Superfluid Density in Infinite-Layer Nickelates
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory（斯坦福材料能源科学研究所，SLAC国家加速器实验室）；Department of Physics, Stanford University（斯坦福大学物理系）；Department of Applied Physics, Stanford University（斯坦福大学应用物理系）；Department of Physics and Astronomy, University of Rochester（罗切斯特大学物理与天文学系）
Structural phase transition, $s_{\pm}$-wave pairing and magnetic stripe order in the bilayered nickelate superconductor La$_3$Ni$_2$O$_7$ under pressure
Following the discovery of superconductivity in the cuprates and the seminal work by Anderson, the theoretical efforts to understand high-temperature superconductivity have been focusing to a large extent on a simple model: the one-band Hubbard model. However, superconducting cuprates need to be doped, and the doped holes go into the oxygen orbitals. This requires a more elaborate multi-band model such as the three-orbital Emery model. The recently discovered nickelate superconductors appear, at first glance, to be even more complicated multi-orbital systems. Here, we analyse this multi-orbita…
Infinite-layer nickelates present a new family of potential unconventional superconductors. A key open question is the superconducting pairing symmetry. We present low-temperature measurements of the London penetration depth in optimally doped La_{0.8}Sr_{0.2}NiO_{2}, Pr_{0.8}Sr_{0.2}NiO_{2}, and Nd_{0.8}Sr_{0.2}NiO_{2}. For La and Pr-nickelates, the superfluid density shows a quadratic temperature dependence, indicating nodal superconductivity in the presence of disorder. Nd-nickelate exhibits complex low-temperature behavior, which we attribute to magnetic impurities. These results are consi…
Despite the structural resemblance of certain cuprate and nickelate parent compounds there is a striking spread of $T_c$ among such transition metal oxide superconductors. We adopt a minimal two-orbital $e_g$ model which covers cuprates and nickelate heterostructures in different parametric limits, and analyse its superconducting instabilities. The joint consideration of interactions, doping, Fermiology, and in particular the $e_g$ orbital splitting allows us to explain the strongly differing pairing propensities in cuprate and nickelate superconductors.
We give a brief review of the Mott-Kondo scenario and its consequence in the recently-discovered infinite-layer nickelate superconductors. We argue that the parent state is a self-doped Mott insulator and propose an effective $t$-$J$-$K$ model to account for its low-energy properties. At small doping, the model describes a low carrier density Kondo system with incoherent Kondo scattering at finite temperatures, in good agreement with experimental observation of the logarithmic temperature dependence of electric resistivity. Upon increasing Sr doping, the model predicts a breakdown of the Kondo…
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory（斯坦福材料能源科学研究所，SLAC国家加速器实验室）；Department of Physics, Stanford University（斯坦福大学物理系）；Department of Applied Physics, Stanford University（斯坦福大学应用物理系）；School of Applied and Engineering Physics, Cornell University（康奈尔大学应用与工程物理学院）；Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory（斯坦福同步辐射光源，SLAC国家加速器实验室）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Kavli Institute at Cornell for Nanoscale Technology, Cornell University（康奈尔大学卡弗里纳米技术研究所）；Geballe Laboratory for Advanced Materials, Stanford University（斯坦福大学盖巴尔先进材料实验室）；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）
Pairing Mechanism in Bilayer Nickelate La$_3$Ni$_2$O$_7$ Superconductors
Institute for Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；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）；New Cornerstone Science Laboratory, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所新基石科学实验室）
Recently discovered superconductivity in hole-doped nickelate Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ has attracted intensive attention in the field. An immediate question is how to improve its superconducting properties. Guided by the key characteristics of electronic structures of the cuprates and the nickelates, we propose that nickel chalcogenides with a similar lattice structure should be a promising family of materials. Using NdNiS$_2$ as an example, through first-principle structural optimization and phonon calculation, we find this particular crystal structure a stable one. We justify our proposal…
Heterostructuring as Gateway to Electron Doping of Nickelate Superconductors
Northwest University（西北大学）；University of Hyogo（兵库大学）；Kyushu Institute of Technology（九州工业大学）；Soochow University（苏州大学）；Universität Würzburg（维尔茨堡大学）；Southeast University（东南大学）；University of Science and Technology of China（中国科学技术大学）；TU Wien（维也纳工业大学）
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）
Electronic structure, dimer physics, orbital-selective behavior, and magnetic tendencies in the bilayer nickelate superconductor La$_3$Ni$_2$O$_7$ under pressure
基于{\it ab initio}技术，研究了双层La$_3$Ni$_2$O$_7$在压力下的电子结构与磁性，揭示了其由$d_{3z^2-r^2}$轨道形成的二聚体晶格、双轨道最小模型、异常的轨道间跃迁及主导的自旋条纹序。
Parameters dependent superconducting transition temperature in high temperature superconductors
School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Key Laboratory of Multiscale Spin Physics(Ministry of Education), Beijing Normal University（北京师范大学多尺度自旋物理教育部重点实验室）；New Cornerstone Science Laboratory, Department of Physics, School of Science, Westlake University（西湖大学理学院物理学系新基石科学实验室）；Institute for Theoretical Sciences, Westlake University（西湖大学理论科学研究院）；Key Laboratory for Quantum Materials of Zhejiang Province, School of Science, Westlake University（西湖大学理学院浙江省量子材料重点实验室）；Institute of Natural Sciences, Westlake Institute for Advanced Study（西湖高等研究院自然科学研究院）
The recent discovery of superconductivity in oxygen-reduced monovalent nickelates has raised a new platform for the study of unconventional superconductivity, with similarities and differences with the cuprate high temperature superconductors. In this paper we investigate the family of infinite-layer nickelates $R$NiO$_2$ with rare-earth $R$ spanning across the lanthanide series, introducing a new and non-trivial "knob" with which to tune nickelate superconductivity. When traversing from La to Lu, the out-of-plane lattice constant decreases dramatically with an accompanying increase of Ni $ d_…
