I13-1-Coherence
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Diamond Proposal Number(s):
[34164]
Open Access
Abstract: X-ray ptychography is a robust microscopy technique with nanoscale resolution that requires a spatially and temporally coherent illumination. In a typical setup, the temporal coherence requirements are satisfied by monochromating the x-ray source, e.g., using a crystal monochromator. Recent studies have shown that energy resolving, or hyperspectral, detectors can to some extent replace the role of the monochromator to perform, e.g., edge-subtraction ptychographic imaging with broadband radiation in a single acquisition. Scaling this capability from two dimensions (2D) to three dimensions (3D), and from a single absorption edge to multiple edges, is critical for its applications in structural and elemental characterisation. The method is hitherto limited by the inherently lower maximum count rate of hyperspectral detectors and the chromaticity of the optics often used in x-ray ptychography experiments, namely Fresnel zone plates. In this work, we design an optimized broadband spectroscopic ptychography setup and use it to perform 3D hyperspectral imaging of particles of battery material containing various percentages of nickel, manganese, cobalt (NMC). We show that we can identify different compositions based on their spectral response. We discuss the results and provide guidelines for future exploitation of the method in laboratory settings.
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Jun 2025
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[30698]
Open Access
Abstract: Through laser-heated diamond anvil cell experiments, we synthesize a series of rubidium superhydrides and explore their properties with synchrotron x-ray powder diffraction and Raman spectroscopy measurements, combined with density functional theory calculations. Upon heating rubidium monohydride embedded in H2 at a pressure of 18 GPa, we form RbH9−I, which is stable upon decompression down to 8.7 GPa, the lowest stability pressure of any known superhydride. At 22 GPa, another polymorph, RbH9−II is synthesised at high temperature. Unique to the Rb-H system among binary metal hydrides is that further compression does not promote the formation of polyhydrides with higher hydrogen content. Instead, heating above 87 GPa yields RbH5, which exhibits two polymorphs (RbH5−I and RbH5−II). All of the crystal structures comprise a complex network of quasimolecular H2 units and H− anions, with RbH5 providing the first experimental evidence of linear H−
3 anions.
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May 2025
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Jiarui
Li
,
Daniel
Jost
,
Ta
Tang
,
Ruohan
Wang
,
Yong
Zhong
,
Zhuoyu
Chen
,
Mirian
Garcia-Fernandez
,
Jonathan
Pelliciari
,
Valentina
Bisogni
,
Brian
Moritz
,
Ke-Jin
Zhou
,
Yao
Wang
,
Thomas P.
Devereaux
,
Wei-Sheng
Lee
,
Zhi-Xun
Shen
Diamond Proposal Number(s):
[32900]
Abstract: Recent photoemission experiments on the quasi-one-dimensional Ba-based cuprates suggest that doped holes experience an attractive potential not captured using the simple Hubbard model. This observation has garnered significant attention due to its potential relevance to Cooper pair formation in high-𝑇𝑐 cuprate superconductors. To scrutinize this assertion, we examined signatures of such an attractive potential in doped 1D cuprates Ba2CuO3+𝛿 by measuring the dispersion of the 2-spinon excitations using Cu 𝐿3-edge resonant inelastic x-ray scattering (RIXS). Upon doping, the 2-spinon excitations appear to weaken, with a shift of the minimal position corresponding to the nesting vector of the Fermi points, 𝑞𝐹. Notably, we find that the energy scale of the 2-spinons near the Brillouin zone boundary is substantially softened compared to that predicted by the Hubbard model in one dimension. Such a discrepancy implies missing ingredients, which lends support for the presence of an additional attractive potential between holes.
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Apr 2025
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I05-ARPES
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Ola Kenji
Forslund
,
Xiaoxiong
Liu
,
Soohyeon
Shin
,
Chun
Lin
,
Masafumi
Horio
,
Qisi
Wang
,
Kevin
Kramer
,
Saumya
Mukherjee
,
Timur
Kim
,
Cephise
Cacho
,
Chennan
Wang
,
Tian
Shang
,
Victor
Ukleev
,
Jonathan S.
White
,
Pascal
Puphal
,
Yasmine
Sassa
,
Ekaterina
Pomjakushina
,
Titus
Neupert
,
Johan
Chang
Diamond Proposal Number(s):
[22091]
Abstract: The anomalous Hall effect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent of a magnetic field, the AHE requires spontaneous TRSB but has proven hard to probe due to averaging over domains. The anomalous component of the Hall effect is thus frequently derived from extrapolating the magnetic field dependence of the Hall response. We show that discerning whether the AHE is an intrinsic property of the field-free system becomes intricate in the presence of strong magnetic fluctuations. As a study case, we use the Weyl semimetal PrAlGe, where TRSB can be toggled via a ferromagnetic transition, providing a transparent view of the AHE’s topological origin. Through a combination of thermodynamic, transport, and muon spin relaxation measurements, we contrast the behavior below the ferromagnetic transition temperature to that of strong magnetic fluctuations above. Our results on PrAlGe provide general insights into the interpretation of anomalous Hall signals in systems where TRSB is debated, such as families of kagome metals or certain transition metal dichalcogenides.
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Mar 2025
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I09-Surface and Interface Structural Analysis
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H. J.
Elmers
,
O.
Tkach
,
Y.
Lytvynenko
,
P.
Yogi
,
M.
Schmitt
,
D.
Biswas
,
J.
Liu
,
S. V.
Chernov
,
Quynh
Nguyen
,
M.
Hoesch
,
D.
Kutnyakhov
,
N.
Wind
,
L.
Wenthaus
,
M.
Scholz
,
K.
Rossnagel
,
A.
Gloskovskii
,
C.
Schlueter
,
A.
Winkelmann
,
A. A.
Haghighirad
,
T.-L.
Lee
,
M.
Sing
,
R.
Claessen
,
M.
Le Tacon
,
J.
Demsar
,
G.
Schönhense
,
O.
Fedchenko
Diamond Proposal Number(s):
[33765]
Abstract: Using x-ray photoelectron diffraction (XPD) and angle-resolved photoemission spectroscopy, we study photoemission intensity changes related to changes in the geometric and electronic structure in the kagome metal CsV3Sb5 upon transition to an unconventional charge density wave (CDW) state. The XPD patterns reveal the presence of a chiral atomic structure in the CDW phase. Furthermore, using circularly polarized x-rays, we have found a pronounced nontrivial circular dichroism in the angular distribution of the valence band photoemission in the CDW phase, indicating a chirality of the electronic structure. This observation is consistent with the proposed orbital loop current order. In view of a negligible spontaneous Kerr signal in recent magneto-optical studies, the results suggest an antiferromagnetic coupling of the orbital magnetic moments along the 𝑐 axis. While the inherent structural chirality may also induce circular dichroism, the observed asymmetry values seem to be too large in the case of the weak structural distortions caused by the CDW.
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Mar 2025
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I10-Beamline for Advanced Dichroism - scattering
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M.
Gomilšek
,
T. j.
Hicken
,
M. n.
Wilson
,
K. J. A.
Franke
,
B. M.
Huddart
,
A.
Štefančič
,
S. J. R.
Holt
,
G.
Balakrishnan
,
D. A.
Mayoh
,
M. t.
Birch
,
S. H.
Moody
,
H.
Luetkens
,
Z.
Guguchia
,
M. t. F.
Telling
,
P. J.
Baker
,
S. J.
Clark
,
T.
Lancaster
Open Access
Abstract: Skyrmions are particlelike vortices of magnetization with nontrivial topology, which are usually stabilized by Dzyaloshinskii-Moriya interactions (DMI) in noncentrosymmetric bulk materials. Exceptions are centrosymmetric Gd- and Eu-based skyrmion-lattice (SL) hosts with zero DMI, where both the SL stabilization mechanisms and magnetic ground states remain controversial. We address these here by investigating both the static and dynamical spin properties of the centrosymmetric SL host Gd2PdSi3 using muon spectroscopy. We find that spin fluctuations in the noncoplanar SL phase are highly anisotropic, implying that spin anisotropy plays a prominent role in stabilizing this phase. We also observe strongly anisotropic spin dynamics in the ground-state (IC-1) incommensurate magnetic phase of the material, indicating that it hosts a meronlike multi-𝑞 structure. In contrast, the higher-field, coplanar IC-2 phase is found to be single 𝑞 with nearly isotropic spin dynamics.
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Jan 2025
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I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[34423, 34827]
Abstract: We performed a pump-probe experiment on the chiral magnet Cu2OSeO3 to study the relaxation dynamics of its noncollinear magnetic orders, employing a millisecond magnetic field pulse as the pump and resonant elastic x-ray scattering as the probe. Our findings reveal that the system requires ∼0.2 s to stabilize after the perturbation applied to both the conical and skyrmion lattice phase, which is significantly slower than the typical nanosecond timescale observed in micromagnetics. This prolonged relaxation is attributed to the formation and slow dissipation of local topological defects, such as emergent monopoles. By unveiling the experimental lifetime of these emergent singularities in a noncollinear magnetic system, our study highlights a universal relaxation mechanism in solitonic textures within the slow dynamics regime, offering new insights into topological physics and advanced information storage solutions.
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Oct 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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S.
Agrestini
,
F.
Borgatti
,
P.
Florio
,
J.
Frassineti
,
D.
Fiore Mosca
,
Q.
Faure
,
B.
Detlefs
,
C. j.
Sahle
,
S.
Francoual
,
J.
Choi
,
Mirian
Garcia-Fernandez
,
K.-J.
Zhou
,
V. f.
Mitrović
,
P. m.
Woodward
,
G.
Ghiringhelli
,
C.
Franchini
,
F.
Boscherini
,
S.
Sanna
,
M.
Moretti Sala
Open Access
Abstract: A supposedly nonmagnetic 5𝑑1 double perovskite oxide is investigated by a combination of spectroscopic and theoretical methods, namely, resonant inelastic x-ray scattering, x-ray absorption spectroscopy, magnetic circular dichroism, and multiplet ligand-field calculations. We found that the large spin-orbit coupling admixes the 5𝑑 𝑡2𝑔 and 𝑒𝑔 orbitals, covalency raises the 5𝑑 population well above the nominal value, and the local symmetry is lower than 𝑂ℎ. The obtained electronic interactions account for the finite magnetic moment of Os in this compound and, in general, of 5𝑑1 ions. Our results provide direct evidence of elusive Jahn-Teller distortions, hinting at a strong electron-lattice coupling.
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Aug 2024
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I05-ARPES
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Yuyang
Dong
,
Yosuke
Arai
,
Kenta
Kuroda
,
Masayuki
Ochi
,
Natsumi
Tanaka
,
Yuxuan
Wan
,
Matthew D.
Watson
,
Timur K.
Kim
,
Cephise
Cacho
,
Makoto
Hashimoto
,
Donghui
Lu
,
Yuji
Aoki
,
Tatsuma D.
Matsuda
,
Takeshi
Kondo
Diamond Proposal Number(s):
[30646, 28930, 25416]
Abstract: The magnetic skyrmions generated in a centrosymmetric crystal were recently first discovered in Gd2PdSi3. In light of this, we observe the electronic structure by angle-resolved photoemission spectroscopy and unveil its direct relationship with the magnetism in this compound. The Fermi surface and band dispersions are demonstrated to have a good agreement with the density functional theory calculations carried out with careful consideration of the crystal superstructure. Most importantly, we find that the three-dimensional Fermi surface has extended nesting which matches well the 𝒒 vector of the magnetic order detected by recent scattering measurements. The consistency we find among angle-resolved photoemission spectroscopy, density functional theory, and the scattering measurements suggests the Ruderman-Kittel-Kasuya-Yosida interaction involving itinerant electrons to be the formation mechanism of skyrmions in Gd2PdSi3.
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Jul 2024
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I05-ARPES
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Jonas
Erhardt
,
Cedric
Schmitt
,
Philipp
Eck
,
Matthias
Schmitt
,
Philipp
Kessler
,
Kyungchan
Lee
,
Timur
Kim
,
Cephise
Cacho
,
Iulia
Cojocariu
,
Daniel
Baranowski
,
Vitaliy
Feyer
,
Louis
Veyrat
,
Giorgio
Sangiovanni
,
Ralph
Claessen
,
Simon
Moser
Diamond Proposal Number(s):
[30583]
Abstract: The demonstration of a topological band inversion constitutes the most elementary proof of a quantum spin Hall insulator (QSHI). On a fundamental level, such an inverted band gap is intrinsically related to the bulk Berry curvature, a gauge-invariant fingerprint of the wave function’s quantum geometric properties in Hilbert space. Intimately tied to orbital angular momentum (OAM), the Berry curvature can be, in principle, extracted from circular dichroism in angle-resolved photoemission spectroscopy (CD-ARPES), were it not for interfering final state photoelectron emission channels that obscure the initial state OAM signature. Here, we outline a full-experimental strategy to avoid such interference artifacts and isolate the clean OAM from the CD-ARPES response. Bench-marking this strategy for the recently discovered atomic monolayer system indenene, we demonstrate its distinct QSHI character and establish CD-ARPES as a scalable bulk probe to experimentally classify the topology of two-dimensional quantum materials with time reversal symmetry.
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May 2024
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