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 194βΒ±β3βmV at 10βmAβcmβ2, which is 41βmV 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 3βd 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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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 π΄-site ordered SmBaMn2β’O6 through a combination of RIXS and soft-x-ray resonant elastic scattering measurements. We confirm the existence of OO at πͺ = (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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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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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-πc 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 πΏ3 edge to investigate the superconducting gap in the overdoped cuprate Bi2β’Sr2β’Ca2β’Cu3β’O10+πΏ (πcβ’=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 πc, indicative of superconducting-gap formation. This suppression is most pronounced at small momentum transfers [
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πβ₯
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β€0.18 r.l.u. (reciprocal lattice units)] and corresponds to a gap size of approximately 2β’Ξ0βΌ130 meV. Comparison with theoretical calculations of the momentum-dependent charge susceptibility supports a π-wave symmetry of the superconducting gap, while an isotropic π -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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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 Sm1βxβyEuxCayNiO2 (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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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 πΏCDWβ0.23β0.35 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 πΏCDW. CDFs are present up to β300K and have relatively short correlation lengths of πβ20Γ
. Here we use Cu-πΏ3 and O-πΎ resonant inelastic x-ray scattering (RIXS) to study the doping dependence of CDW and CDFs in La2βπ₯β’Srπ₯β’CuO4. 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 πΏ4β’π-CDWβ0.24 and two CDF components with πΏ4β’π-CDFβ0.24 and πΏ3β’π-CDFβ0.30. We find that for πβππ the CDW coexists with the CDFs for dopings near π₯=πβ1/8. The 4β’π-CDW disappears beyond π₯=0.16 and the 4β’π-CDF beyond π₯=0.19, leaving only a weak 3β’π-CDF at the highest doping studied, π₯=0.22. Our data suggest that low-energy charge fluctuations exist up to doping π₯=0.19=πβ
, 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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Zubia
Hasan
,
Grace A.
Pan
,
Harrison
Labollita
,
Austin
Kaczmarek
,
Suk Hyun
Sung
,
Shekhar
Sharma
,
Purnima P.
Balakrishnan
,
Edward
Mercer
,
Vivek
Bhartiya
,
Alpha T.
N'Diaye
,
Zaher
Salman
,
Thomas
Prokscha
,
Andreas
Suter
,
Alexander J.
Grutter
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Jonathan
Pelliciari
,
Valentina
Bisogni
,
Ismail
El Baggari
,
Darrell G.
Schlom
,
Matthew R.
Barone
,
Charles M.
Brooks
,
Katja C.
Nowack
,
Antia S.
Botana
,
Brendan D.
Faeth
,
Alberto
De La Torre
,
Julia A.
Mundy
Diamond Proposal Number(s):
[34236]
Open Access
Abstract: Geometrically frustrated lattices can display a range of correlated phenomena, ranging from spin frustration and charge order to dispersionless flat bands due to quantum interference. One particularly compelling family of such materials is the half-valence spinel LiB2O4 materials. On the B-site frustrated pyrochlore sublattice, the interplay of correlated metallic behavior and charge frustration leads to a superconducting state in LiTi2O4 and heavy fermion behavior in LiV2O4. To date, however, LiTi2O4 has primarily been understood as a conventional BCS superconductor despite a lattice structure that could host more exotic ground states. Here, we present a multimodal investigation of LiTi2O4, combining ARPES, RIXS, proximate magnetic probes, and ab-initio many-body theoretical calculations. Our data reveals a novel mobile polaronic ground state with spectroscopic signatures that underlie co-dominant electron-phonon coupling and electron-electron correlations also found in the lightly doped cuprates. The cooperation between the two interaction scales distinguishes LiTi2O4 from other superconducting titanates, suggesting an unconventional origin to superconductivity in LiTi2O4. Our work deepens our understanding of the rare interplay of electron-electron correlations and electron-phonon coupling in unconventional superconducting systems. In particular, our work identifies the geometrically frustrated, mixed-valence spinel family as an under-explored platform for discovering unconventional, correlated ground states.
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Jan 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Ke-Jin
Zhou
,
Qiushi
Huang
,
Mirian
Garcia-Fernandez
,
Yeqi
Zhuang
,
Stefano
Agrestini
,
Shengyou
Wen
,
Thomas
Rice
,
Sahil
Tippireddy
,
Jaewon
Choi
,
Andrew
Walters
,
Igor V.
Kozhevnikov
,
Zhe
Zhang
,
Runze
Qi
,
Zhong
Zhang
,
Hongchang
Wang
,
Zhanshan
Wang
Open Access
Abstract: Resonant inelastic X-ray scattering (RIXS) is a photon-in/photon-out spectroscopic technique which has become increasingly important for the condensed matter physics community. The development of the RIXS instrumentation in soft X-ray and hard X-ray range facilitated the research in 3d and 5d transition metal (TM)-based materials, respectively. However, the tender X-ray (2000β3000βeV) RIXS covering most of 4d TM-based materials severely falls behind due to the lack of high-performance energy dispersive optics. Here, we demonstrate the design and fabrication of a laterally graded multilayer grating (MLG) optics for the establishment of the tender RIXS at the I21 RIXS beamline in Diamond Light Source. The successful implementation of the MLG boosts the photon flux by more than an order of magnitude at the Sulfur K-edge (2475βeV) and the Ru L3-edge (2838βeV) in comparison to the solution of a single-layer coated grating (SLG). More importantly, MLG retains the high energy resolution of the SLG design (~10,000) and works continuously across the full range of 2000β3000βeV. It renders the I21 beamline as the very first RIXS facility in the world that covers both soft and tender X-rays (280β3000βeV) using a grating-based spectrometer for a wide range of science applications.
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Jan 2026
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Optics
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Arindam
Majhi
,
Wadwan
Singhapong
,
Wai Jue
Tan
,
Andrey
Sokolov
,
Stefano
Agrestini
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Andrew C.
Walters
,
Chris
Bowen
,
Alexander J. G.
Lunt
,
Hongchang
Wang
,
Kawal J.
Sawhney
Open Access
Abstract: Laterally graded multilayer optics play an important role in advanced X-ray applications, enabling precise control of beam properties for spectroscopic and focusing techniques. The Multilayer Deposition System (MDS) at Diamond Light Source (DLS) has demonstrated its ability to fabricate highly precise laterally graded X-ray optics. Developing such optics is challenging due to stringent requirements for precise lateral thickness variations and sagittal uniformity, achieved through optimized substrate speed profiles and advanced mask design. This study presents a comprehensive investigation into the design, fabrication, and characterization of laterally graded multilayers. An adjustable mask design improves sagittal uniformity and reduces optimization times. The structural and optical performance of the multilayers is evaluated, confirming their suitability for synchrotron applications. Two types of laterally graded multilayers were developed: one with a constant lateral gradient (0.005 nm/mm) for O-K edge polarizers, achieving sagittal thickness variations of approximately 0.3β0.4% across an 80 mm substrate, and another featuring a strong variable gradient from 0.037 to 0.112 nm/mm, designed to match the elliptical periodicity profile. The constant gradient multilayer polarizer has been successfully implemented on the state-of-the-art I21 beamline at DLS, highlighting the MDS's role in producing next-generation X-ray optics that meet the stringent demands of synchrotron beamlines.
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Jan 2026
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