I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xiaoyang
Chen
,
Wenliang
Zhang
,
Fei
Peng
,
Ting
Cui
,
Guangdi
Zhou
,
Zezhong
Li
,
Jaewon
Choi
,
Lizhi
Xu
,
Yiu-Fung
Chiu
,
Stefano
Agrestini
,
Sahil
Tippireddy
,
Haoliang
Huang
,
Heng
Wang
,
Xianfeng
Wu
,
Peng
Li
,
Jin-Feng
Jia
,
Mirian
Garcia-Fernandez
,
Yi
Lu
,
Er-Jia
Guo
,
Qi-Kun
Xue
,
Zhuoyu
Chen
,
Donglai
Feng
,
Ke-Jin
Zhou
Diamond Proposal Number(s):
[42637]
Open Access
Abstract: The recent discovery of Ruddlesden-Popper (RP) nickelate thin-film superconductors has opened a new frontier in unconventional superconductivity. Its realization requires both compressive epitaxial strain and highly oxidative growth conditions, yet the microscopic pathway from the parent phase to the superconducting phase remains elusive. Here, X-ray absorption spectra and resonant inelastic X-ray scattering are employed to track this evolution by independently tuning strain and oxygen content in (La,Pr)3Ni2O7 − δ thin films. We uncover a remarkable two-step narrative. First, signatures of delocalization emerge: Spectral weight transfers from a “Upper Hubbard”-like peak to the hole-like peak associated with O 2pz state, and in parallel, the initially localized Ni
orbital becomes more itinerant followed by the broadening and weakening of dd orbital excitations. Second, as itinerancy increases, long-range spin-density-wave (SDW) order is suppressed in both intensity and correlation length, indicating direct competition with superconductivity. Yet, short-range magnons persist: they become damped but their bandwidth stays unchanged. Our results paint a coherent picture that both strain and oxygenation drive the RP bilayer nickelates towards the superconducting instability, where the O 2pz and Ni
orbitals become delocalized. Concomitantly, the long-range magnetic order loses coherence and gets suppressed. These findings establish an orbital-selective route to RP nickelate superconductivity, in which the emergence and progressive delocalization of the interlayer
-2pz-
channel and the robust short-range magnons upon the melting of SDW order are prerequisites, providing strong constraints for theory and the roadmap for designing nickelate superconductors.
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Aug 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Grace A.
Pan
,
Dan Ferenc
Segedin
,
Sophia F. R.
Tenhuisen
,
Lopa
Bhatt
,
Harrison
Labollita
,
Abigail Y.
Jiang
,
Qi
Song
,
Ari B.
Turkiewicz
,
Denitsa R.
Baykusheva
,
Abhishek
Nag
,
Stefano
Agrestini
,
Ke-Jin
Zhou
,
Jonathan
Pelliciari
,
Valentina
Bisogni
,
Hua
Zhou
,
Mark P. M.
Dean
,
Hanjong
Paik
,
David A.
Muller
,
Lena F.
Kourkoutis
,
Charles M.
Brooks
,
Matteo
Mitrano
,
Antia S.
Botana
,
Berit H.
Goodge
,
Julia A.
Mundy
Diamond Proposal Number(s):
[27484]
Abstract: The discovery of superconductivity in square-planar nickelates has offered a rich materials platform to explore the origins of high-temperature superconductivity. However, experimental investigations have largely been limited to the infinite-layer RNiO2 (R, rare earth) nickelates. We constructed a phase diagram of multilayer square-planar Ndn+1NinO2n+2 compounds and found signatures of superconductivity for dimensionality n = 4 to 8. Upon decreasing n, the superconducting anisotropy evolves owing to 4f electron effects, and electronic structure characteristics approach cuprate-like behavior. Magnetic fluctuations persist from within the superconducting regime and into the overdoped, nonsuperconducting regime. The superconducting regime overlaps with that of chemically doped infinite-layer nickelates, demonstrating underlying commonalities as well as differences across varying structural realizations of square-planar nickelates. Our work establishes this layered template for creating new nickel-based superconductors.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[24600, 30866]
Open Access
Abstract: The electron in a solid can be considered a bound state of the three independent, fundamental degrees of freedom creating quasiparticles: spinons, carrying the electron spin; plasmons, carrying the collective charge mode; and orbitons, carrying its orbital degree of freedom. These fundamental degrees of freedom could form ordering states in which dynamics or collective motions could occur and manifest as low-energy excitations. The exotic properties that appear in the materials exhibiting these electronic orderings are associated with these low-energy excitations. Although the orbital order (OO) and its coupling to the spin system creates very interesting phenomena, the microscopic origin of OO has been much less explored than other electronic properties as it is very difficult to directly access experimentally. Due to the recent improvement in energy resolution and flux, soft-x-ray resonant inelastic scattering (RIXS) allows for a reexamination of orbital excitations in manganites. Here, we present a study of low-energy excitations in half doped 𝐴-site ordered SmBaMn2O6 through a combination of RIXS and soft-x-ray resonant elastic scattering measurements. We confirm the existence of OO at 𝐪 = (0.25, 0.25, 0) and find various low-energy excitations below 200 meV. While several excitations can be assigned to be of magnetic and phononic origin, a group of excitations between 80 and 200 meV show a temperature dependence closely following that of the OO, making them possible candidates for orbitons.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Kunhao
Li
,
Qizhi
Li
,
Changwei
Zou
,
Jaewon
Choi
,
Chaohui
Yin
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Shilong
Zhang
,
Chengtian
Lin
,
Xingjiang
Zhou
,
Ke-Jin
Zhou
,
Yi
Lu
,
Yingying
Peng
Diamond Proposal Number(s):
[30361]
Abstract: The superconducting gap is a characteristic feature of high-𝑇c superconductors and provides crucial information on the pairing mechanism underlying high-temperature superconductivity. Here, we employ high-resolution resonant inelastic x-ray scattering (RIXS) at the Cu 𝐿3 edge to investigate the superconducting gap in the overdoped cuprate Bi2Sr2Ca2Cu3O10+𝛿 (𝑇c=107K). By analyzing antisymmetrized, temperature-dependent RIXS spectra over a range of in-plane momentum transfers, we observe a clear suppression of low-energy spectral weight below 𝑇c, indicative of superconducting-gap formation. This suppression is most pronounced at small momentum transfers [
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𝒒∥
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≤0.18 r.l.u. (reciprocal lattice units)] and corresponds to a gap size of approximately 2Δ0∼130 meV. Comparison with theoretical calculations of the momentum-dependent charge susceptibility supports a 𝑑-wave symmetry of the superconducting gap, while an isotropic 𝑠-wave gap fails to reproduce key experimental features. These findings establish RIXS as a powerful, bulk-sensitive probe of superconducting-gap symmetry and highlight its utility for studying materials beyond the reach of surface-sensitive techniques such as ARPES and STM.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xin
Zhang
,
Qiyun
Wang
,
Qi
Zhang
,
Haoyin
Zhong
,
Chao
Wu
,
Baorui
Jia
,
Junchen
Yu
,
Ke-Jin
Zhou
,
Yuanjie
Li
,
Yong-Wei
Zhang
,
Zhi Gen
Yu
,
Shibo
Xi
,
Xiaopeng
Wang
,
Junmin
Xue
Diamond Proposal Number(s):
[35048]
Open Access
Abstract: Introducing oxygen redox chemistry into cobalt oxyhydroxide effectively enhances catalytic activity by enabling direct O-O coupling, thereby bypassing the rate-limiting *OOH step in the conventional adsorbate evolution mechanism. However, the key challenge is to preserve the accessibility of non-bonding oxygen states while maintaining cobalt-oxygen covalency. Here we show that light irradiation triggers ligand-to-metal charge transfer in sulfur-treated cobalt oxyhydroxide (S-CoOOH), generating non-bonding oxygen states. These states then couple with adjacent ones to form direct O-O bonds. Through this way, the sulfur-treated sample performs enhanced OER activity under light, achieving an overpotential of 194 ± 3 mV at 10 mA cm−2, which is 41 mV lower than in the dark. Further analysis reveals that light-induced oxygen redox activity is confined to the edge of catalyst. This activity originates from electron transitions from (M-O) to non-overlapping regions of Co 3 d and 4p orbitals, driven by high-spin Co3+ at the edge. This work highlights the critical role of light in inducing non-bonding oxygen states in transition metal-based catalysts and guides the development of oxygen-redox electrocatalysts.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xunyang
Hong
,
Yuetong
Wu
,
Izabela
Bialo
,
Ying
Chan
,
Sze Tung
Li
,
Leonardo
Martinelli
,
Orion
Gerguri
,
Annabella
Drewanowski
,
Qiang
Gao
,
Xiaolin
Ren
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Alice
Galdi
,
Darrell G.
Schlom
,
Kyle M.
Shen
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Nicholas B.
Brookes
,
Henrikm.
Ronnow
,
Qisi
Wang
,
Johan
Chang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Optimization of unconventional superconductivity involves a balance of interaction strengths. Precise determination of correlation strength across different material families is therefore important. Here, we present a combined X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) study of infinite-layer PrNiO2 and SrCuO2 that enables fair comparison of their interaction strengths. For both compounds, we study the orbital and magnetic excitations and extract their dispersions along high-symmetry directions. Using a single-band Hubbard model and including physically plausible assumptions about higher-order exchange interactions, we estimate the correlation factor U/t for both compounds. A key finding is that despite the prediction of a smaller Coulomb repulsion U, PrNiO2 exhibits a correlation strength U/t that is 20% stronger than that of its isostructural cuprate counterpart SrCuO2. This indicates that moderation of the correlation strength may further optimize superconductivity in nickelates.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[29150]
Open Access
Abstract: Cuprate superconductors show various collective charge correlations that are intimately connected with their electronic properties. In particular, charge order in the form of an incommensurate charge density wave (CDW) order with an in-plane wave vector 𝛿CDW≈0.23–0.35 reciprocal lattice units appears to be universally present. In addition to CDW, dynamic charge density fluctuations (CDFs) are also present with wave vectors comparable to 𝛿CDW. CDFs are present up to ≈300K and have relatively short correlation lengths of 𝜉≈20Å. Here we use Cu-𝐿3 and O-𝐾 resonant inelastic x-ray scattering (RIXS) to study the doping dependence of CDW and CDFs in La2−𝑥Sr𝑥CuO4. We fit our data with (quasi)elastic peaks resulting from the CDW and up to four inelastic modes associated with oxygen phonons that can be strongly coupled to the CDFs. Our analysis allows us to separate the charge correlations into three components: the CDW with wave vector 𝛿4𝑎-CDW≈0.24 and two CDF components with 𝛿4𝑎-CDF≈0.24 and 𝛿3𝑎-CDF≈0.30. We find that for 𝑇≈𝑇𝑐 the CDW coexists with the CDFs for dopings near 𝑥=𝑝≈1/8. The 4𝑎-CDW disappears beyond 𝑥=0.16 and the 4𝑎-CDF beyond 𝑥=0.19, leaving only a weak 3𝑎-CDF at the highest doping studied, 𝑥=0.22. Our data suggest that low-energy charge fluctuations exist up to doping 𝑥=0.19=𝑝★, where the pseudogap disappears; however, we find no evidence that they are associated with a quantum critical point.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Yujie
Yan
,
Ying
Chan
,
Xunyang
Hong
,
S. Lin Er
Chow
,
Zhaoyang
Luo
,
Yuehong
Li
,
Tianren
Wang
,
Yuetong
Wu
,
Izabela
Bialo
,
Nurul
Fitriyah
,
Saurav
Prakash
,
Xing
Gao
,
King Yau
Yip
,
Qiang
Gao
,
Xiaolin
Ren
,
Jaewon
Choi
,
Ganesha
Channagowdra
,
Jun
Okamoto
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Liang
Si
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Hsiao-Yu
Huang
,
Di-Jing
Huang
,
Johan
Chang
,
Ariando
Ariando
,
Qisi
Wang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: The recent discovery of high-temperature superconductivity in hole-doped SmNiO2, exhibiting the record-high transition temperature Tc among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni L-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm1−x−yEuxCayNiO2 (SECNO). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECNO samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of Tc in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately 20%. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with Tc, highlighting essential differences in their superconducting mechanisms.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Abstract: This work develops and applies a linear-response TDDFT framework for core-level spectroscopy. It implements the formalism in CRYSTAL, then merges TDDFT electronic transition properties with the linear-coupling vibronic model to simulate the quasi-elastic energy range of RIXS. The framework is first tested on simple benchmarks and then used to interpret the nitrogen K-edge NEXAFS and RIXS of TCNQ embedded in TTF–TCNQ.
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May 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Gaurav C.
Pandey
,
Ashok S.
Menon
,
Valeria
Calani San Miguel
,
José J.
Arroyo‐gómez
,
Harry
Gillions
,
Rebecca
Sellers
,
Matthew J. W.
Ogley
,
Eleni
Fiamegkou
,
Satish
Bolloju
,
Sahil
Tippireddy
,
Mirian
Garcia-Fernandez
,
Steven
Huband
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[38432]
Open Access
Abstract: The electrochemical performance of single-crystalline (SC) Ni-rich layered oxide cathodes is fundamentally limited by bulk Li+ diffusion within micrometre-sized particles. During high-voltage cycling—necessary for high-energy applications—intraparticle Li+ diffusion is further impeded by oxygen-loss-induced surface reconstruction from the layered phase to spinel/rock-salt structures. Therefore, to fully understand how bulk Li+ transport kinetics influences electrochemical degradation, it is necessary to establish the correlation between surface reconstruction and bulk delithiation during the anisotropic structural evolution (i.e., expansion of the layers followed by their contraction) of the cathode particles during long-term cycling. In this work, we accomplish this using multi-rate operando X-ray diffraction studies of SC Ni-rich layered oxide cathodes aged under different voltage windows in single-layer pouch full cells. We quantify how increased surface reconstruction leads to greater heterogeneity in bulk delithiation, thereby promoting phase separation and exacerbating electrochemical capacity fade. These results provide a direct mechanistic link between surface degradation and bulk delithiation in such cathodes and offer a framework for non-destructively probing kinetics-dependent degradation under practically relevant conditions to guide strategies for improved cycling stability.
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May 2026
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