The 4th International Workshop on
High-Tc Nickelate Superconductivity：
May 10–13, 2026 , APCTP,Pohang, Korea
May 10–13, 2026 , APCTP,Pohang, Korea
Content
AbstractBook
Harold Hwang
Stanford University
Unconventional superconductivity in proximity to various strongly correlated electronic phases has been a recurring theme in materials as diverse as heavy fermion compounds, cuprates, pnictides, and twisted bilayer graphene. Here we will briefly introduce superconducting infinite-layer nickelates, and present our recent studies of this system. These include the evolution of the superfluid density (arXiv:2603.05606) and optical conductivity (arXiv:2602.09567), and high-pressure studies of freestanding membranes (arXiv:2604.09525).
Meng Wang
Sun Yat-Sen University
TBD
Thomas Deveraux
Stanford University
In this talk I will present a theoretical study of polarization dependent x-ray absorption and resonant inelastic x-ray scattering on bilayer La₃Ni₂O₇. Investigating the polarization dependence can reveal detailed information of three-spin polaron involving holes on adjacent Ni dz² orbitals via hole states on bridging oxygens. This locked polaron freezes the dz² hole states, leaving the dx²−y² orbitals to participate in superconductivity, akin to the single layer nickelates as well as cuprates. Spectroscopic signatures will be discussed and examined.
Hai-Hu Wen
Department of Physics, Nanjing University, Nanjing 210093, China
The recent discovery of high temperature superconductivity in nickelate systems has generated tremendous interests in the community. We have successfully synthesized the superconducting thin films of La₂PrNi₂O₇ with Tcⁱᵒⁿˢᵉᵗ = 41.5 K at ambient pressure, and found that the Tcⁱᵒⁿˢᵉᵗ can be enhanced to above 60 K under pressure. Our theoretical calculations yield a cooperative enhancement of magnetic fluctuations between and within the layers and increased metallicity under pressure. These findings highlight the critical role of the interplay between interlayer and intralayer electronic correlations in bilayer nickelate superconductors.
We also successfully measured the single particle tunneling spectrum after we expose the superconducting layer by using the tip-excavation technique. A dominant gap at about 19 meV is observed and a kink structure is observed at about 6–8 meV, the later is interpreted as a second smaller gap. The fittings based on the Dynes model indicate that the dominant gap should have an s+−-pairing symmetry. The uniform spectra across a relatively long distance suggests a good coherent state in the bilayer nickelates, which is different from the cuprate superconductors and indicates the definite involvement of the less correlated 3dx²−y² orbital.
References
[1] Qing Li, Jianping Sun, Steffen Bötzel, Mengjun Ou, Zhe-Ning Xiang, Frank Lechermann, Bosen Wang, Yi Wang, Ying-Jie Zhang, Jinguang Cheng, Ilya M. Eremin & Hai-Hu Wen. Nature Communications 17, 3276 (2026).
[2] Shengtai Fan, Mengjun Ou, Marius Scholten, Qing Li, Zhiyuan Shang, Yi Wang, Jiasen Xu, Huan Yang, Ilya M. Eremin, Hai-Hu Wen. arXiv: 2506.01788.
Jinguang Cheng
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
E-mail: jgcheng@iphy.ac.cn
The discovery of superconductivity in infinite-layer nickelate (ILN) Nd₀.₈Sr₀.₂NiO₂ in 2019 marked the beginning of so-called nickel age of superconductivity. The recent observation of high-temperature superconductivity approaching 40 K in the Sm-based ILNs and magnetic-field-induced re-entrant superconductivity in Eu-doped ILNs has garnered significant attention in this field. In this talk, I will present our recent experimental progress on the Sm-based and Eu-doped ILNs. For the Sm-based INLs, our high-pressure measurements revealed an enhancement of Tc reaching ~50 K at 7 GPa and the presence of anomalous resistance peak near Tcⁱᵒⁿˢᵉᵗ above 9 GPa presumably due to enhanced magnetic scattering. For the Eu-doped ILN system, we synthesized a series of Nd₁₋ₓEuₓNiO₂ samples with nominal concentrations from x = 0.1 to 0.4 and observed field-enhanced re-entrant superconductivity in both underdoped (x = 0.2) and over-doped (x = 0.4) samples with Tcᶻᵉʳᵒ below 10 K. Some peculiar features will be discussed.
References
[1] Chow, S. L. E., Luo, Z. & Ariando, A. Bulk superconductivity near 40 K in hole-doped SmNiO₂ at ambient pressure. Nature 642, 58–63 (2025).
[2] Yang, M. et al. Enhanced superconductivity and mixed-dimensional behaviour in infinite-layer samarium nickelate thin films. Nat. Commun., (2026).
[3] Yang, M. et al. Robust field re-entrant superconductivity in ferromagnetic infinite-layer rare-earth nickelates. arXiv:2508.14666 (2025).
[4] Vu, D. et al. Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd₁₋ₓEuₓNiO₂ thin films. Nat. Commun., (2026).
[5] Rubi, K. et al. Extreme magnetic field-boosted superconductivity in a high-temperature superconductor. arXiv:2508.16290 (2025).
[6] Varbaro, L. et al. Paramagnetically driven superconducting re-entrance in Eu-doped infinite layer nickelates. arXiv:2601.19473 (2026).
[7] Han, H. et al. A chemical avenue to manipulate field-reentrant superconducting rivalries in infinite layer nickelates. arXiv:2511.22026 (2025).
Di Peng
Shanghai Advanced Research in Physical Sciences
The discovery of high-temperature superconducting (HTS) materials has profoundly transcended the established framework of conventional Bardeen-Cooper-Schrieffer (BCS) theory, with their anomalous superconducting properties providing an ideal platform for probing the mechanisms of unconventional superconductivity. Recent breakthroughs in nickelate superconductors have further extended this research frontier, delivering a novel experimental paradigm to decode the longstanding puzzle of high-temperature superconductivity. Hydrostatic pressure, distinguished by its uniform stress distribution and negligible lattice distortion artifacts, enables faithful capture of the intrinsic pressure-driven material responses, serving as a critical bridge between ambient-pressure physics and extreme-condition physics. Here, by combining high-pressure diffraction, high-pressure electrical transport, and high-pressure magnetometry under isostatic pressure, we systematically explore the structural evolution and superconducting characteristics of bilayer, mixed-bilayer, and trilayer nickelate superconductors under high pressure. From these measurements, we establish a comprehensive phase diagram in pressure-temperature (P-T) space that encompasses structural, density-wave, and superconducting phases, and elucidate the mechanisms underpinning the pressure-tuned competition and transition between distinct superconducting phases. Furthermore, using this hydrostatic pressure platform, we report the first observation of nearly isotropic, strong three-dimensional interlayer coupling in trilayer nickelate superconductors, alongside the d-wave pairing symmetry in bilayer nickelate systems. Our work provides key experimental underpinnings to advance the fundamental understanding of nickelate superconductivity.
Ilya Eremin
Ruhr-University Bochum, Germany
Recent Scanning Tunneling Microscopy (STM) experiments measuring the superconducting gap features in thin films of superconducting bilayer nickelates La₂PrNi₂O₇ at ambient pressure and compressive strain paved the way to study the Cooper-pairing models and the band-selective identification of the gap features in these systems. Here, using the realistic two-orbital bilayer model and the continuum Green's function formalism, we theoretically analyze orbital and band-selective local density of states as well as the corresponding STM spectra. We find that the multiorbital character and the spatial dependence of the Wannier functions leads to the spectra developing characteristic features depending on the position of the scanning tunneling microscope's tip. This allows for a band-resolved analysis of the superconducting coherence peaks and scattering momenta. We identify a clear path for experimental measurements to not only identify the debated incipiency of the γ-band, but also identification of the coherence peaks' band origins via distance dependent measurements of the local density of states and its corrections through impurity scattering.
Yijun Yu
Fudan University
Understanding how superconductivity emerges and collapses in correlated electron systems remains a central challenge in condensed matter physics. As a recently discovered member of the high temperature superconductor family, bilayer nickelates provide a new opportunity to examining this problem. Their pronounced sensitivity to oxygen stoichiometry, while posing challenges for stabilizing superconductivity, simultaneously offers an effective control parameter for tuning electronic phases. In this talk, we will discuss the observation of a superconducting half-dome in compressively strained bilayer nickelate thin films under continuous tuning of oxygen stoichiometry. The half-dome emerges consistently across samples with different rare-earth combinations, with or without alkaline-earth doping, revealing a general feature of the bilayer nickelate phase diagram.
Zhuoyu Chen
Southern University of Science and Technology
We introduce gigantic-oxidative atomic-layer-by-layer epitaxy to synthesize Ruddlesden-Popper (RP) bilayer and superstructure nickelates. We report achieving ambient-pressure superconductivity in monolayer-bilayer and bilayer-trilayer superstructures, together with an enhanced onset Tc in the bilayers. With cryogenic ultrahigh vacuum (UHV) sample transfer, ARPES data reveals an underlying dz²-related band at the Fermi level in the superconducting structures, with nodeless superconducting gaps.
Bai Yang Wang
Stanford University; SLAC National Lab
bwang87@stanford.edu
The discovery of superconductivity in bulk nickelates under high pressure marked a major advance in the field. The subsequent realization of superconductivity at ambient pressure in compressively strained bilayer nickelate thin films now enables direct spectroscopic interrogation of the superconducting phase by angle-resolved photoemission spectroscopy (ARPES). In this talk, I will present a systematic in situ ARPES study of such films, spanning Ca doping, oxygen stoichiometry, and thickness. The electronic structure, robust against oxygen-vacancy disorder and surface termination, exhibits systematic strain-driven evolution and is consistent with theoretical descriptions in the intermediate-correlation regime. I will further discuss detailed analyses of the α and γ band dispersions, providing key constraints on the electronic ingredients underlying bilayer nickelate superconductivity.
Berit H. Goodge
Max Planck Institute for Chemical Physics of Solids
The origin of superconductivity in Ruddlesden-Popper nickelates remains a key question, particularly regarding the importance of certain band alignments and related hopping parameters which are sensitive to structural distortions. Recently, compressive epitaxial strain has been shown to stabilize superconductivity in bilayer La₃Ni₂O₇, potentially mimicking that observed in bulk single crystals under high hydrostatic pressure. In bulk samples, previous proposals highlighted c-axis compression as a key driver of low-energy Ni 3d bands near the Fermi level. Intriguingly, this lattice parameter instead expands in compressively strained superconducting films. Other proposals have suggested sensitive dependence of the superconducting pairing symmetry on subtle changes in the nickel-oxygen bonding environment, calling for precise measurements of the local atomic structure in these compounds. Multislice electron ptychography (MEP) provides a method to precisely extract reliable oxygen atomic positions with deep sub-Ångström spatial resolution. Here, we leverage MEP to quantitatively investigate a full series of epitaxial thin films spanning compressive to tensile strain. We track the strain-dependent evolution of key structural parameters such as Ni-O bond lengths, bond angles, and octahedra. This structural parameterization provides crucial input for accurate theoretical modeling in these compounds which is not accessible by other measurements. We further introduce a density functional theory (DFT) framework for strain decomposition to identify key commonalities in the lattice and electronic structures of superconducting sample geometries in both bulk and thin films.
References
[1] Ko et al. Nature 638, 935 (2025).
[2] Sun et al. Nature 621, 493 (2023).
[3] Chen et al. Science 372, 826 (2021).
[4] Bhatt et al. Nature (2026).
Motoki Osada
1 Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo, Japan
2 Department of Applied Physics, University of Tokyo, Hongo, Tokyo, Japan
The recent discovery of high-transition temperature Tc superconductivity near 80 K in pressurized La₃Ni₂O₇ bulk crystals has attracted keen attention due to its characteristic energy diagram involving d3z²–r² and dx²–y² orbitals. Subsequently, superconductivity near 40 K was reported at ambient pressure in compressively strained films. These findings provide valuable insights into the orbital contributions and interlayer interactions in double NiO₆ octahedra. Whereas hydrostatic pressure drives nearly isotropic lattice compression, epitaxial strain imposes biaxial in-plane constraints with out-of-plane elongation. Combining epitaxial strain control with external hydrostatic pressure offers a unique platform to disentangle anisotropic and isotropic lattice effects on superconductivity. In particular, investigating how isotropic compression influences films that already exhibit superconductivity under strong epitaxial strain provides crucial insight into the underlying mechanisms of high-Tc superconductivity. Within this context, we demonstrate a comprehensive strain-high-pressure approach in bilayer nickelate thin films grown on various oxide substrates, and apply pressures up to 20 GPa using a cubic-anvil cell. Details of transport measurements under ambient- and high-pressure conditions will be discussed in this presentation.
References
[1] H. Sun, et al. Nature, 621, 493 (2023).
[2] H. Sakakibara, et al. Phys. Rev. Lett. 132, 106002 (2024).
[3] E. K. Ko, et al. Nature, 638, 935 (2025).
[4] G. Zhou, et al. Nature, 640, 641 (2025).
[5] M. Osada, et al. Commun. Phys. 8, 251 (2025).
Wenjie Sun, Zhicheng Jiang, Bo Hao, Maosen Wang, Shengjun Yan, Hongyi Zhang, Haoying Sun, Zhengtai Liu, Zhengbin Gu, Dianxiang Ji, Jian Zhou, Dawei Shen, Donglai Feng, Yuefeng Nie
1 National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093, China.
2 National Synchrotron Radiation Laboratory and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230026, China.
3 Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201210, China.
4 New Cornerstone Science Laboratory, Hefei National Laboratory, Hefei, 230088, China
The discovery of Ruddlesden-Popper nickelate superconductors provides a new platform for investigating unconventional high-temperature superconductivity. In this study, we employed oxide molecular beam epitaxy (OMBE) and angle-resolved photoemission spectroscopy (ARPES) to explore the superconducting phase diagram and electronic band structure of La₃₋ₓSrₓNi₂O₇₋δ thin films. Through systematic control of Sr doping and oxygen content, we observed a superconducting dome with an intriguing sign reversal of the Hall coefficient near the maximum superconducting transition temperature. ARPES measurements reveal the presence of Ni 3dx²−y²-derived α and β bands near the Fermi level, which show nodeless leading edge shifts below the superconducting transition temperature. Furthermore, the γ band remains below the Fermi level in superconducting samples. These findings provide crucial experimental insights into the superconducting mechanism in bilayer nickelates.
References
Haobo, et al. Nat. Mater. 24, 1756 (2025)
M.S. Wang, et al. Phys. Rev. Lett. 136, 066002 (2026)
W.J. Sun, et al. arXiv:2507.07409 (2025)
Junfeng He
University of Science and Technology of China
The discovery of superconductivity in Ruddlesden-Popper (RP) bilayer nickelate films under ambient pressure provides an unprecedented opportunity to directly investigate the electronic structure and energy scales of the superconducting state. By developing an ultra-high vacuum cryogenic quenching and transfer technique, we have successfully carried out angle-resolved photoemission spectroscopy (ARPES) measurements on the superconducting films. In this talk, we will present our recent results on (La,Pr,Sm)₃Ni₂O₇ thin films epitaxially grown on SrLaAlO₄ substrates with a focus on the band structure and electronic energy scales.
Ariando Ariando
National University of Singapore
Magnetism is generally detrimental to superconductivity, but in unconventional systems the two coexist and give rise to exotic phenomena such as spin-triplet pairing and field-induced superconductivity. In the infinite-layer nickelate series SmEuCaNiO₂ (SECNO), samples with specific Eu concentrations exhibit field-reentrant superconductivity, which has been attributed to Jaccarino-Peter (JP) compensation driven by Eu²⁺ magnetic moments.
In this talk, I will further present a striking observation of a hysteretic superconducting state in SECNO, emerging below 2 K with coercive field exceeding 1 T, unprecedented among known ferromagnetic superconductors or superconducting heterostructures. Complementary evidence, together with the Eu-concentration dependence, points to an intrinsic underlying ferromagnetic ground state spanning the SECNO series. By revealing the coexistence of ferromagnetism and superconductivity, our work provides critical insights into the interplay among ferromagnetic order, JP compensation, and Eu doping in SECNO. This field-history-dependent superconducting state enriches the fundamental physics of correlated oxides.
Danfeng Li
Department of Physics, City University of Hong Kong, Kowloon, Hong Kong SAR, China
Infinite-layer nickelates have emerged as a frontier platform for studying unconventional superconductivity beyond the cuprates. In this talk, I will present our recent advances on samarium-based infinite-layer nickelate thin films, which exhibit enhanced superconductivity and a mixed two- and three-dimensional superconducting character arising from strong coupling between rare-earth 5d and Ni 3d orbitals. I will further highlight our finding of a robust field-induced re-entrant superconductivity in heavily Eu-doped Sm₀.₉₅₋ₓCa₀.₀₅EuₓNiO₂, where superconductivity suppressed at low magnetic fields and re-emerges at higher fields. This exotic state results from the interplay between NiO-plane superconductivity and Eu²⁺-sublattice magnetism, revealing a unique coexistence of magnetism and superconductivity. These findings demonstrate how rare-earth-site engineering and magnetic-field tuning provide powerful routes for realising and manipulating magnetically enabled high-field superconductivity.
References
[1] M. Yang, H. Wang, J. Tang, J. Luo et al., Enhanced Superconductivity and Mixed-dimensional Behaviour in Infinite-layer Samarium Nickelate Thin Films, Nature Communications 17, 2761 (2026).
[2] M. Yang, J. Tang, X. Wu, H. Wang et al., Field re-entrant superconductivity in Eu-doped infinite-layer nickelates, arXiv:2508.14666 (2025).
Peter Wahl
University of St. Andrews
Strong electronic correlations can drive spontaneous spatial organization of charge and spin degrees of freedom in quantum materials. Within the framework of the Mott–Hubbard model, one prominent example is the formation of stripe-ordered phases, in which metallic charge-rich channels coexist with antiferromagnetic regions. Such stripe order has been widely discussed in the context of cuprate high-temperature superconductors and has recently attracted renewed attention in nickelate systems.
I will discuss atomic-scale imaging of stripe order in the trilayer nickelate La₄Ni₃O₁₀. Our measurements directly resolve both the magnetic and charge order associated with the stripe phase. The stripes exhibit a four–unit-cell periodicity, closely resembling those observed in cuprates, and are accompanied by the opening of a near-complete ∼66 meV gap at the Fermi level.
Beyond static imaging, we demonstrate that the stripe phase exhibits dynamic behavior: tunnelling electrons can induce discrete phase slips once the excitation energy exceeds ∼20 meV. This enables visualization of stripe dynamics in real space at the atomic scale.
Our results establish the presence of strongly correlated stripe physics in lanthanum nickelates and highlight its potential relevance for understanding superconductivity in the broader nickelate family.
Tao Wu
University of Science and Technology of China
The discovery of superconductivity in Ruddlesden-Popper (RP) nickelates Rₙ₊₁NiₙO₃ₙ₊₁ (R = rare earth) under high pressure provides a new platform to understand the underlying physics of high-temperature superconductivity. Previous transport measurements under pressure suggest a notable correlation between pressure-induced high-temperature superconductivity and a density-wave (DW) state at low pressures. Identifying the nature of the DW state is a prerequisite for decoding the superconducting mechanism in this new family of high-temperature superconductivity. In this talk, I will introduce our recent NMR results on the nature of DW state in trilayer nickelate La₄Ni₃O₁₀.
Karsten Held
Technische Universität Wien
The discovery of superconductivity in infinite-layer nickelates marked a new age of superconductivity: the nickel age. Using density functional theory, dynamical mean-field theory and dynamical vertex approximation (DΓA), we successfully predicted the phase diagram Tc vs. Sr-doping of Nd₁₋ₓSrₓNiO₂ with - for an unconventional superconductor - unprecedented accuracy with defect-free films synthesized only 3 years later. Also the normal state spin spectrum well agrees with resonant inelastic x-ray spectroscopy (RIXS) and the one-particle spectrum with angular-resolved photoemission spectroscopy (ARPES), including waterfalls. With this excellent agreement to later experiments, we can now with some confidence predict the phase diagram of finite-layer nickelates and that infinite-layer nickelates have a much higher Tc under 100 GPa of pressure even without any chemical doping.
This work has been supported by the ERC project 101201037 and the FWF project I5398.
References
[1] D. Li et al., Nature 572, 624 (2019).
[2] G. Rohringer et al., Rev. Mod. Phys. 90, 25003 (2018).
[3] M. Kitatani et al., npj Quantum Materials 5, 59 (2020).
[4] K. Lee et al., Nature 619, 288 (2023).
[5] L. Si et al., Phys. Rev. Res. 6, 043104 (2024).
[6] P. Worm et al., Phys. Rev. B 109, 235123 (2024).
[7] J. Krsnik and K. Held, Nature Comm. 16, 255 (2025).
[8] A. Hausoel et al., npj Quantum Materials 10, 69 (2025).
[9] S. Di Cataldo et al., Nature Comm. 15, 3952 (2024).
Ryotaro Arita
University of Tokyo & RIKEN
Understanding structural phase diagrams at finite temperatures is a central challenge in quantum materials, particularly when lattice symmetry plays a key role in emergent phenomena such as superconductivity. In this talk, we present a first-principles approach to determine the pressure–temperature (p–T) phase diagram based on finite-temperature structural optimization incorporating anharmonic lattice dynamics.
Our method extends the self-consistent phonon (SCP) framework to enable efficient free-energy minimization with respect to atomic structures at finite temperatures, even for phase transitions accompanied by changes in unit-cell size. This is achieved by combining supercell-based phonon treatments with an improved structural optimization algorithm, allowing robust and accurate determination of thermodynamic stability.
Applying this framework to the bilayer nickelate La₃Ni₂O₇, we directly compute the p–T phase diagram from first principles. We find that the phase boundary between the low-symmetry Amam phase and the high-symmetry I4/mmm phase exhibits a clear temperature dependence, forming an approximately linear boundary with a negative slope.
This work demonstrates that finite-temperature structural optimization provides a powerful and general route to predicting phase diagrams of complex materials. We expect that the resulting phase diagram will offer a crucial foundation for elucidating the pairing mechanism.
Ref: arXiv: 2512.08251
Sangkook Choi
Korea Institute for Advanced Study
Quantum information science is a surging frontier of physical science. By creating quantum states and utilizing them as quantum bits (qubits), it promises vastly improved performance over what we have achieved during the 20th century.
Quantum materials are a class of materials of which properties can be explained by only quantum physics. When their quantum nature is due to electron-electron interaction, quantum materials give rise to a rich tableau of novel physics. These so-called correlated quantum materials can be utilized as “semiconductors” for quantum information science.
However, quantitative understanding correlated quantum materials properties is one of the grand challenges in the field of quantum materials. Correlated quantum materials preclude simple explanations and computationally simple methods based on Landau’s Fermi liquid theory, such as density functional theory.
In this talk, I will present ab initio fully self-consistent GW plus Extended Dynamical Mean Field Theory (GW+EDMFT) approach—a robust ab initio framework designed to capture the interplay of non-local correlations and local dynamics. I will validate this method through its application to several correlated quantum materials, highlighting the unique physical insights gained from this state-of-the-art computational approach.
Kazuhiko Kuroki
Osaka University
There exists a correspondence between the two-orbital Hubbard model and the bilayer Hubbard model, in which superconductivity is optimized in an incipient-band regime in both cases. In the two-orbital system, the orbital level offset ΔE plays a role analogous to the interlayer hopping in bilayer systems, and superconductivity is enhanced for large ΔE. We refer to such a two-orbital model as an orbital-space bilayer model (OSBM). In this study, we theoretically propose that a reduced bilayer nickelate La₃Ni₂O₆ can be a candidate for a superconductor described by OSBM when an appropriate amount of holes is doped. By constructing a tight-binding model based on first principles calculations, a large ΔE between the Ni dx²−y² and the other d orbitals is obtained due to the absence of outer apical oxygens. Furthermore, our fluctuation exchange approximation calculations indicate the emergence of s±-wave superconductivity driven by interorbital interactions in an incipient-band situation, where the superconducting gap function changes its sign between the dx²−y² and other d orbital bands. We also investigate the energetic and dynamical stability of the crystal structure under atomic substitution and pressure. Although La₃Ni₂O₇ and La₃Ni₂O₆ share similar chemical formula, our study shows that an entirely different pairing mechanism can take place in the latter.
References
[1] H. Shinaoka et al., Phys. Rev. B 92, 195126 (2015).
[2] K. Yamazaki et al., Phys. Rev. Res. 2, 033356 (2020).
[3] N. Kitamine et al., Phys. Rev. Res. 2, 042032 (2020).
[4] H. Sakakibara et al., Phys. Rev. B 111, 224511 (2025).
[5] S. Kamiyama et al., arXiv:2603.11771.
Guang-Ming Zhang
ShanghaiTech University and Tsinghua University, China
Motivated with experimental resistivity and Hall coefficient data in the normal state of the infinite-layer nickelate superconductors, we proposed that its parent compound is a self-doped Mott insulator and an effective t-J-K model can account for its low-energy properties. At small hole doping, the model describes a low carrier density Kondo system with incoherent Kondo scattering, in good agreement with experimental observation of the logarithmic temperature dependence of electric resistivity and Hall coefficient.
For the high-Tc superconductivity of La₃Ni₂O₇ under high pressure, we proposed another multi-orbital model including both 3dz² and 3dx²−y² orbital electrons of the nickel cations: the main feature is that the 3dz² electrons form inter-layer bonding and anti-bonding bands via the apical oxygen anions between the two layers, while the 3dx²−y² electrons hybridize with the 3dz² bonding electrons within each NiO₂ plane. The chemical potential difference of these two orbitals ensures that the 3dz² orbitals are close to half-filling and the 3dx²−y² orbitals are near quarter-filling. The strong on-site Hubbard repulsion of the 3dz² bonding electrons gives rise to an effective inter-layer antiferromagnetic spin super-exchange. Applying pressure introduced holes on the 3dz² bonding electrons with the same amount of electrons doped on the 3dx²−y² orbitals, leading to a cooperative multi-orbital superconductivity.
References
G. -M. Zhang, Y. F. Yang, F. C. Zhang, Physical Review B 101, 020501 (2020).
Z. Wang, G. -M. Zhang, Y. F. Yang, F. C. Zhang, Phys. Rev. B 102, 220501 (2020)
H. Sun, …, G. -M. Zhang and M. Wang, Nature 621, 493 (2023).
Y. Shen, M. P. Qin, G. -M. Zhang, Chinese Physical Letters 40, 127401 (2023).
Y. F. Yang, G. -M. Zhang, F. C. Zhang, Physical Review B 108, L201108 (2023).
Daoxin Yao
Sun Yat-Sen University
Recently, 1212 La₅Ni₃O₁₁, 1313 La₃Ni₂O₇ and 2323 La₇Ni₅O₁₇ have been successfully synthesized and show superconductivity experimentally. They show different behaviors compared with the pure RP nickelate superconductors. For example, 1212 La₅Ni₃O₁₁ exhibits a dome-shaped pressure dependence with the highest Tc≈64 K, in contrast to the previously reported right-triangle-like behavior observed in the 2222 La₃Ni₂O₇. A much lower Tc ≈ 3.6 K was observed in the pressurized 1313 La₃Ni₂O₇, compared with Tc≈ 80 K in the 2222 La₃Ni₂O₇ reported previously. Here, using density functional theory (DFT)/ DFT+DMFT and random phase approximation (RPA) calculations, we systematically study the electronic properties and superconducting mechanism of 1212 La₅Ni₃O₁₁ and 1313 La₃Ni₂O₇. Our calculations yield a band structure including two nearly decoupled sets of sub-band structures, with one set originating from the bilayer/trilayer subsystem and the other from the single-layer one. RPA-based analysis demonstrates that SC in these materials occurs primarily within the bilayer/trilayer subsystem exhibiting an s± wave pairing symmetry similar to that observed in pressurized La₃Ni₂O₇ and La₄Ni₃O₁₀, while the single-layer subsystem mainly serves as a bridge facilitating the inter-bilayer phase coherence through the interlayer Josephson coupling (IJC). Since the IJC thus attained is extremely weak, it experiences a prominent enhancement under pressure, leading to the distinct behaviors of the bulk Tc such as the dome-shaped pressure dependence in 1212 La₅Ni₃O₁₁. We suggest that the high-Tc phase in the RP La₃Ni₂O₇ family should be attributed to the 2222 La₃Ni₂O₇ rather than the 1313 La₃Ni₂O₇. Our work establishes design rules for achieving enhanced phase coherence and high-Tc in hybrid nickelate superconductors and other layered transition-metal oxides.
References
Ming Zhang, Cui-Qun Chen, Dao-Xin Yao, Fan Yang, Sci. China Phys. Mech. Astron. 69, 257411 (2026).
Cui-Qun Chen, Ming Zhang, Fan Yang, Dao-Xin Yao, arXiv: 2604.21533 (2026)
Giniyat Khaliullin
Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
We present a microscopic model for superconductivity in bilayer nickelates. The model reveals the physical mechanism by which in-plane compressive strain stabilizes the superconducting state against charge- and magnetic order. Cooper pairing is mediated by weakly dispersive singlet-triplet excitations (triplons) of interlayer spin dimers. The calculated hierarchy of superconducting gaps on different bands and their angular dependence are in good agreement with experimental data. The global phase diagram of the model is also discussed.
References
G. Khaliullin and J. Chaloupka, Phys. Rev. B 113, L041115 (2026).
H. Liu and G. Khaliullin, arXiv:2602.23989.
Frank Lechermann
Ruhr-Universität Bochum
The discovery of superconductivity in selected layer nickelates, either in thin-film form or under high pressures, has boosted the research on these transition-metal oxides to a new level. Finding relations among the different nickelate superconductors and looking for new possible candidate systems within this large family of compounds, is a timely task. In this talk, three different layered oxides will be discussed that are driven to an insulating state by strong electron correlation. First-principles many-body theory proves as a reliable tool to reveal the intriguing multiorbital physics at play, respectively. Understanding these insulating states on a deeper level, drawing the good connections and realizing them in experiment may be helpful toward completing the bigger picture of nickelate physics. Moreover, those states might be novel startings point for the stabilization of unconventional superconductivity.
Weiqiang Chen
Southern University of Science and Technology
TBD
Zhan Wang
Institute of Physics, Chinese Academy of Sciences
Bilayer nickelate La₃Ni₂O₇ offers a new setting to study the interplay between Mottness, multi-orbital physics, and superconductivity. We show that a bilayer Hubbard model supports a molecular Mott state driven by strong interaction and interlayer coupling, which becomes self-doped through charge transfer to higher-energy bands as the interlayer coupling is reduced. Guided by this picture, we study a two-band t-J model and find an orbital-selective d-wave superconducting state emerging only from the itinerant orbital, while the quasi-localized orbital suppresses pairing by promoting local inter-orbital bound states. These results support a picture of La₃Ni₂O₇ as a self-doped molecular Mott system and suggest that suppressing localized dz²-derived states may help enhance superconductivity.
Xingjiang Zhou
Institute of Physics, Chinese Academy of Sciences, Beijing, China
We combine high-resolution angle-resolved photoemission spectroscopy with tight-binding model simulation to investigate the electronic structure of the trilayer Ruddlesden-Popper nickelate La₄Ni₃O₁₀. We provide the first experimental evidence of band splitting induced by interlayer coupling and further resolve the momentum-dependent density wave gap structures along all the Fermi surfaces. Our findings identify the mirror-selective Fermi surface nesting as the origin of the interlayer antiferromagnetic spin density wave and demonstrate the dominant role of Ni-3dz² orbitals in the low-energy physics of La₄Ni₃O₁₀. These results provide a fundamental framework for understanding the magnetic interactions and high-temperature superconductivity mechanism in the Ruddlesden-Popper nickelate family.
Donglai Feng
ShanghaiTech University, Shanghai, China
The discovery of superconductivity in infinite-layer (IL) nickelates has opened a new frontier for investigating the mechanisms of high-temperature superconductivity. Although their Ni dx²−y² band resembles that of cuprates, the presence of additional Fermi surface pockets and multi-orbital contributions has led to competing theories and unsettled debates. A central challenge has been the lack of direct experimental knowledge of their low-energy electronic structure. Using angle-resolved photoemission spectroscopy (ARPES), including polarization-dependent and resonant techniques, we have now resolved the key electronic features of optimally-doped IL nickelates and their parent compounds LaNiO₂ and NdNiO₂. Our measurements show that the additional electron-like pocket arises primarily from interstitial s states with electride-like character, rather than rare-earth 5d or 4f orbitals, and that the rare-earth element tunes Ni-derived bands through a chemical pressure effect. These findings establish the orbital origin of the extra Fermi surfaces, clarify the role of rare-earth ions in shaping the band structure, and demonstrate the existence of electride-like interstitial carriers in a correlated oxide system. In hole-doped La₀.₈Ca₀.₂NiO₂, we further observe momentum-dependent spectral weight suppression and marginal-Fermi liquid behavior. Together, they highlight the unique physics of IL nickelates, and provide fresh insight into self-doping and superconductivity in this emergent material family.
References
[1] X. Ding, et al., National Science Review, 11, nwae194 (2024).
[2] Li, C., et al., Physical Review Letters 135: 116501 (2025).
M. Kriener, C. Terakura, A. Kikkawa, Z. Liu, H. Murayama, M. Nakajima, Y. Fujishiro, S. Sasano, R. Ishikawa, N. Shibata, Y. Tokura, Y. Taguchi
1 RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
2 RIKEN Pioneering Research Institute, Wako, 351-0198, Japan
3 Department of Applied Physics, The University of Tokyo, Tokyo 113-865, Japan
4 Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-865, Japan
5 Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, Aichi 456-8587, Japan
6 Tokyo College, The University of Tokyo, Tokyo 113-865, Japan
7 Baton Zone Program, TRIP Headquarters, RIKEN, Wako 351-0198, Japan
Pressurized bilayer nickelates based on La₃Ni₂O₇ have attracted great attention as a new platform for studying unconventional superconductivity. Besides the interest in identifying related superconducting nickelates with possibly higher superconducting transition temperatures Tc and/or lower critical pressures pc required to induce robust superconductivity, there are also persistent experimental problems. These are related to sample quality, such as impurity phase formation and deviations from the oxygen stoichiometry. To address these, we employ a high-pressure synthesis technique which allows (i) to reduce or eliminate impurity phases and (ii) the in-situ use of oxidizing materials to tune the oxygen content.
With this approach we synthesized La₂₋ₓRSrₓNi₂O₇ with R = La (x = 0, 0.1) and Nd (0 ≤ x ≤ 0.2) and studied the distinct effects of modifying the bandwidth (Nd substitution) and the band filling (Sr hole doping). While decreasing the bandwidth in La₂NdNi₂O₇ increases the critical pressure, simultaneous hole doping in La₁.₉NdSr₀.₁Ni₂O₇ shifts the superconducting phase back to lower pressure enabling control over pc. In the nonsuperconducting state, we observe up to three different kinds of anomalies labeled T1, T2 and T3. While the origin of the latter remains elusive, the former two seem related to charge- and spin-density-wave features, respectively, as discussed in the literature. With increasing pressure, T1 is suppressed prior to the first indications of superconductivity, whereas T2 is enhanced. The opposite pressure dependences are in contrast to the cuprates, where such features are often intertwined, highlighting an interesting difference in the electronic ground states of these two families of high-Tc superconductors.
In this talk, we will present our sample growth method and discuss the evolution of the various anomalies and the superconducting phase space as functions of composition, temperature, and pressure.
References
[1] H. Sun et al., Nature 621, 493 (2023)
[2] S. Taniguchi et al., J. Phys. Soc. Jpn. 64, 1644 (1995)
[3] F. Li et al., Phys. Rev. Mater. 8, 053401 (2024)
[4] R. Khasanov et al., Nature Phys. 21, 430 (2025)
[5] M. Kriener et al., arXiv:2604.13875 (2026)
Jiangping Hu
Institute of Physics, Chinese Academy of Sciences
TBD
Hiroya Sakurai
National Institute for Materials Science
The solid-state synthesis of Laₙ₊₁NiₙO₃ₙ₊₁ (n = 2, 3) and related materials is challenging due to competing factors of thermal stability and low reactivity. While the upper limit of the synthesis temperature is restricted by thermal stability, the lower limit—set by sluggish reaction kinetics—requires sufficiently high thermal energy for the system to approach equilibrium. In practice, conventional solid-state reactions often produce a significant density of stacking faults, i.e., deviations in the stacking sequence of perovskite slabs with varying numbers of NiO₆ layers relative to the nominal phase. Such defects must be minimized, as they complicate the electronic states of the samples due to structural inhomogeneity. To address this issue, a modified solid-state synthesis route incorporating hydrogen reduction has been developed to enhance sample homogeneity. This approach is effective even for La-substituted nickelates, despite their narrower synthesis temperature windows compared with La-based parent compounds.
Control of carrier filling represents another key challenge in nickelates. In n = 1 compounds, excess oxygen can be accommodated within the rock-salt layers, suggesting that n = 2 and 3 phases may also host a significant amount of interstitial oxygen. Conversely, oxygen vacancies are known to form preferentially at the inner apical oxygen sites located between adjacent Ni ions along the c-axis. To examine this experimentally, independent sample batches were subjected to either high-oxygen-pressure annealing using a hot isostatic press or annealing in flowing hydrogen. For La₃Ni₂O₇, both excess oxygen and oxygen vacancies were successfully introduced, whereas for La₄Ni₃O₁₀, only oxygen vacancies were observed under the present annealing conditions, with no evidence of excess oxygen incorporation. In both systems, however, the concentrations of excess oxygen and vacancies cannot be tuned continuously due to phase separation. Superconductivity appears to be optimized near stoichiometric compositions. In oxygen-deficient samples, even metallic behavior is suppressed, likely due to Anderson localization with local magnetic moments, highlighting the critical role of inner apical oxygen sites and strong electronic correlations.
In La₃Ni₂O₇, the coexistence of excess oxygen and oxygen vacancies strongly suggests the formation of Frenkel defects, as supported by La NQR measurements. Given the pronounced impact of defects at the inner apical sites, Frenkel defects may reduce the superconducting volume fraction of La₃Ni₂O₇ samples.
References
[1] H. Sakurai and Y. Takano, Superconducting Lanthanum Nickel Oxides with Bilayered and Trilayered Crystal Structures, J. Phys.: Condens. Matter 38 (2026) 073002.
Dawei Shen
National Synchrotron Radiation Laboratory, University of Science and Technology of China, China
dwshen@ustc.edu.cn
Unraveling the interplay between density-wave (DW) instabilities and multi-orbital physics is critical for understanding superconductivity in Ruddlesden-Popper nickelates, yet intrinsic electronic features have been persistently obscured by material inhomogeneity and thus the multi-domain averaging effect. In this talk, I will introduce that we employ micro-focused angle-resolved photoemission spectroscopy (μ-ARPES) on single-domain Pr₄Ni₃O₁₀ to disentangle the complex hierarchy of intrinsic and back-folded bands, explicitly identifying the electronic states driving the DW phase transition. We provide decisive spectroscopic evidence that the low-energy reconstruction is governed by inter-band nesting between the α and β bands. Specifically, we resolve a gap of ∼ 44 meV on the α pocket, a value quantitatively consistent with prior measurements, unifying previously conflicting experimental reports regarding the locus and magnitude of the DW gap. Furthermore, we successfully resolve the long-sought intrinsic trilayer β-band splitting, establishing a critical lower bound for the outer-layer hopping. These results define a coherent microscopic fingerprint for the trilayer nickelates, identifying the specific nesting channels and correlation effects.
Junjie Zhang
Institute of Crystal Materials, Shandong University
Layered nickelates have emerged as a new class of high-Tc superconductors following the discovery of ~80 K superconductivity in bilayer La₃Ni₂O₇ under high pressure (Sun et al Nature 2023). Despite significant progress in the past years, certain fundamental issues still exist, including the mechanism of high-Tc superconductivity, whether it is possible to increase Tc, whether it is possible to prepare single crystals without the need of high oxygen pressure. In this talk, I will present a series of advances in my group. First, we realized the single crystal growth of nickelate superconductors at ambient pressure for the first time, exemplified by La₄Ni₃O₁₀ and La₃Ni₂O₇. After annealing, these crystals superconduct under high pressure. Second, we reveal a strong correlation between the highest Tc under high pressure and the in-plane distortion at ambient pressure. Guided by this insight, we created the new world record of Tc = 96 K for nickelate superconductors. Our work provides an effective strategy for further enhancements of Tc for nickelate superconductors. Last but not least, we designed and synthesized a novel monolayer-bilayer hybrid nickelate, which opens the door to a completely new family of hybrid Ruddlesden-Popper nickelate superconductors.
References
[1] Junjie Zhang et al. China Invention Patent ZL 2023 1 0922576.2 (2023).
[2] Li, F. et al. Flux Growth of Trilayer La₄Ni₃O₁₀ Single Crystals at Ambient Pressure. Cryst. Growth Des. 24, 347-354 (2024).
[3] Li, F. et al. Single-Crystal Structure Determination of Superconducting La₄Ni₃O₁₀-δ under High Pressure. Adv. Mater. 37, e07365 (2025).
[4] Li, F. et al. Bulk superconductivity up to 96 K in pressurized nickelate single crystals. Nature 649, 871-878 (2026).
[5] Li, F. et al. Design and synthesis of three-dimensional hybrid Ruddlesden-Popper nickelate single crystals. Phys. Rev. Mater. 8, 053401 (2024).
Nanlin Wang
Shanghai Jiaotong University
TBD
Matthias Hepting
Max Planck Institute for Solid State Research
In the phase diagram of Ruddlesden–Popper (RP) nickelates, superconductivity occurs in close proximity to charge- and spin-density-wave (DW) order, yet the microscopic nature of these instabilities and their interplay remains unresolved. Central questions concern the orbital composition, symmetry, and gap formation associated with the DW state. Using polarization-resolved Raman scattering on the trilayer nickelate La₄Ni₃O₁₀, we identify characteristic phonon anomalies and a redistribution of electronic spectral weight across the DW transitions. Momentum-selective electronic Raman responses, combined with multiorbital model calculations, indicate a DW-induced gap with an incoherent, non-mean-field-like opening and contributions from both Ni dx²−y² and dz² states. These results address inconsistencies among prior experiments and support a multiorbital description of the DW state. In addition, complementary Raman measurements on the monolayer–trilayer polymorph La₃Ni₂O₇ will be discussed, providing a broader view of how structural complexity within the RP series influences lattice dynamics and intertwined electronic instabilities.
References
[1] A. Suthar et al., arXiv:2508.06443
[2] V. Sundaramurthy et al., arXiv:2512.17583v1
Dong–Hyeon Gim, Chung Ha Park, Kee Hoon Kim
1 Department of Physics & Astronomy, Seoul National University, Seoul 08826, Korea
2 Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
In the first part, we investigate the evolution of polarized electronic response in trilayer nickelate La₄Ni₃O₁₀, reporting a systematic reduction of the incoherent electron continuum across the density wave transition in the A₁g and B₁g representations. Analysis based on the Fermi surface band curvatures points to quasiparticle coherence in momentum positions with dominant dx²−y² orbital character. Our findings establish the symmetry channels and the active role of orbitals involved in the density wave formation, offering important insight into the electronic and magnetic correlations in the nickelate. In the second part, we provide a comprehensive spectroscopic map of the electronic, magnetic, and lattice excitations in La₃Ni₂O₇ at ambient pressure. Upon entering the spin density wave (SDW) state, an electronic spectral gap develops primarily in the s-wave-like A₁g channel, exhibiting a clear isosbestic point. Besides the electronic scattering, we identify separate two-magnon excitations in the B₁g and B₂g channels, a direct signature of incipient Mottness in La₃Ni₂O₇, providing unambiguous evidence for two distinct in-plane spin exchange interactions. Furthermore, we observe the emergence of additional low-energy magnetic modes, revealing the presence of two distinct, coexisting nickel spin moments. Moreover, a clear lattice instability is signaled by an anomalous softening of B₁g phonons that persists through the SDW transition, potentially linked to a valence or bond disproportionation. Collectively, our findings establish a detailed picture of the complex landscape of competing interactions and instabilities in La₃Ni₂O₇, which is essential for an integrated understanding of nickelate superconductors.
References
Dong-Hyeon Kim et al., Phys. Rev. Lett, 135, 136505 (2025).
Dong-Hyeon Kim et al., unpublished (2026)
Yusuke Nomura
Institute for Materials Research, Tohoku University
The quest to understand high-transition temperature (Tc) superconductivity (SC) remains a central issue in condensed matter physics. In this context, the recent discovery of high-Tc SC in La₃Ni₂O₇ has generated significant interest.
As a canonical model hosting high-Tc SC and as a minimal toy model for La₃Ni₂O₇, we investigate the bilayer Hubbard model on a square lattice using state-of-the-art cluster dynamical mean-field theory. Unlike the d-wave SC observed in doped Mott insulators such as cuprates, the bilayer model exhibits s±-wave SC emerging from a correlated band insulator, where dynamical band repulsion drives the insulating behavior. We uncover kinetic-energy-driven SC in a small doping region and its crossover to conventional potential-energy-driven SC. Above Tc, we observe an unusual metallic state with a striking momentum-space dichotomy in the kinetic-energy-driven regime: one Fermi pocket develops a pseudogap while the other becomes nearly incipient.
Despite differences in pairing symmetry and parent insulating states, we identify the strong momentum-space dichotomy as a remarkable commonality between the d-wave SC (antinodal vs. nodal regions) and the s±-wave SC (electron vs. hole pockets). The dichotomy in the bilayer system arises from self-energy differences between bonding and antibonding orbitals, further linking it to orbital-selective physics in iron-based superconductors.
Using a novel method for estimating the coherence length in strongly correlated SC, we reveal that the coherence length of the s±-wave SC is only a few lattice constants, corresponding to ~1 nm in La₃Ni₂O₇, which accounts for the exceptionally high critical field (~100 T) observed experimentally. This localized pairing may be driven by an effective pair-hopping term between bonding and antibonding orbitals, analogous to localized Cooper pairing in fullerides, in which the intramolecular pair-hopping term plays a crucial role.
References
[1] H. Sun et al., Nature 621, 493 (2023).
[2] Y. Nomura, M. Kitatani, S. Sakai, and R. Arita, Phys. Rev. B 112, L020504 (2025).
[3] S. S. Kancharla and S. Okamoto, Phys. Rev. B 75, 193104 (2007).
[4] N. Witt et al., npj Quantum Materials 9, 100 (2024).
[5] Y. Nomura et al., J. Phys. Condens. Matter 28, 153001 (2016).
Rustem Khasanov, Thomas J. Hicken, Hubertus Luetkens, Zurab Guguchia, Dariusz J. Gawryluk, Vignesh Sundaramurthy, Abhi Suthar, Masahiko Isobe, Bernhard Keimer, Giniyat Khaliullin, Matthias Hepting, Pascal Puphal
¹ PSI Center for Neutron and Muon Sciences CNM, 5232 Villigen PSI, Switzerland
² Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
³ 2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
We investigate the magnetic properties of the alternating monolayer–trilayer phase of La₃Ni₂O₇ (1313-La₃Ni₂O₇) by muon-spin rotation/relaxation (μSR) at ambient and hydrostatic pressure. This phase develops incommensurate magnetic order below about 150 K, with a mean ordering temperature of TSDW ≃ 123 K and a transition width of ΔTSDW ≃ 15 K. The abrupt onset of the internal magnetic field indicates a first-order-like transition. Hydrostatic pressure suppresses the magnetic ordering temperature at a rate of dTSDW/dp ≃ −3.9 K/GPa, showing a progressive destabilization of the ordered state. Comparison with the bilayer 2222-La₃Ni₂O₇ and trilayer 3333-La₄Ni₃O₁₀ compounds reveals systematic trends linking pressure response, magnetic incommensurability, and the character of the transition. These results identify 1313-La₃Ni₂O₇ as an intermediate member between the 2222 and 3333 nickelates and provide insight into the interplay of structure, magnetism, and correlations in layered nickelates.