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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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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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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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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Marli R.
Cantarino
,
Rafael M. P.
Teixeira
,
Kevin R.
Pakuszewski
,
Wagner R.
Da Silva Neto
,
Juliana G.
De Abrantes
,
Mirian
Garcia-Fernandez
,
Pascoal G.
Pagliuso
,
Cris
Adriano
,
Claude
Monney
,
Thorsten
Schmitt
,
Eric C.
Andrade
,
Fernando A.
Garcia
Diamond Proposal Number(s):
[33194]
Open Access
Abstract: In doped Hund's metals, such as the iron-based superconductors, effects like charge doping and chemical pressure are often considered the dominant factors. Partial chemical substitution, however, inevitably introduces disorder. Here, we investigate spin excitations in Ba(Fe1−𝑥Cr𝑥)2As2 (CrBFA) by high-resolution resonant inelastic x-ray scattering for samples with 𝑥=0,0.035, and 0.085. In CrBFA, Cr acts as a hole dopant, but also introduces localized spins that compete with Fe-derived magnetic excitations. We found that the Fe-derived magnetic excitations are softened and damped, becoming overdamped for 𝑥=0.085. At this doping level, complementary angle-resolved photoemission spectroscopy measurements show increased electronic localization and a suppression of the nematic 𝑑𝑥𝑧/𝑑𝑦𝑧 band splitting present in the parent compound. We thus propose a localized spin model that explicitly incorporates substitutional disorder and Cr local moments, successfully reproducing our key observations. Our findings reveal a case where disorder dominates over charge doping in the case of a Hund's metal.
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Feb 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 (2000–3000 eV) 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 (2475 eV) and the Ru L3-edge (2838 eV) 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 2000–3000 eV. It renders the I21 beamline as the very first RIXS facility in the world that covers both soft and tender X-rays (280–3000 eV) 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 0.3–0.4% 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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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Open Access
Abstract: Oxygen redox (OR) in Li1.2Ni0.13Co0.13Mn0.54O2 (LRNMC) and Na0.67Mg0.28Mn0.72O2 (NMMO) has been associated with the formation of embedded molecular O2 due to the appearance of their distinctive features in RIXS, while it is unclear whether OR also affects the oxygen left in the lattice. Here we use high-resolution oxygen K-edge resonant inelastic X-ray scattering (RIXS) at threshold excitation (527.5 – 529.5 eV) revealing lattice responses due to OR. We find that both cathodes show pronounced multiphonon progressions, which are either altered or activated upon charging. The first progression, with a fundamental energy loss ∼67-74 meV, matches the A1g lattice-oxygen mode observed by Raman spectroscopy, confirming its bulk origin. The second progression that exhibits a fundamental loss of ∼98 meV appears only at the highest state of charge and is resonant with the new pre-edge states at 527.5 eV. The latter mode emerges concurrently with the characteristic trapped-O2 RIXS signal and is strongly coupled to an occupied electronic band near the Fermi level, indicating that OR may not only contribute to the formation of molecular O2, but also perturbs lattice oxygen states, likely via polaron-forming oxidized lattice oxygen.
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Dec 2025
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[36210]
Open Access
Abstract: Quasiparticles describe collective excitations in many-body systems, and their symmetry classification is of fundamental importance for physical processes such as excited states, transport phenomena, and phase transitions. Recent studies have introduced chirality as an additional degree of freedom in condensed matter physics, leading to a range of novel phenomena. Among these, chiral phonons are of special interest because they carry angular momentum and therefore intrinsically break time reversal symmetry, which non-trivially bridges the spin system with the lattice. Here, we directly prove the presence of chiral phonons in a prototypical polar LiNbO3 crystal. Our demonstration of chiral phonons in a ferroelectric enables in-situ electrical control of momentum-dependent “magnetic” polarization with the reversible phonon handedness. This ferroic control of phonon chirality has substantial potential in the emerging field of chiral phononics, particularly along the associated control of its phonon angular momentum.
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Dec 2025
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