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Emily C.
Mcfarlane
,
Antonio
Sanna
,
Matthew J.
Gilbert
,
Jonas A.
Krieger
,
Mihir
Date
,
Gabriele
Domaine
,
Banabir
Pal
,
Anirban
Chakraborty
,
Pranava K.
Sivakumar
,
Procopios C.
Constantinou
,
Anna
Hartl
,
Enrico G.
Della Valle
,
Camilla
Pellegrini
,
Vladimir N.
Strocov
,
Stuart S. P.
Parkin
,
Niels B. M.
Schroeter
Open Access
Abstract: Superconductivity in the transition-metal dichalcogenide PdTe2 has been attributed to the proximity of a three-dimensional Van Hove singularity to the Fermi level. In isostructural NiTe2, recently used as the weak link in a Josephson diode, a similar Van Hove singularity has been predicted to occur, but superconductivity is mysteriously absent. Using bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy, we reveal that this Van Hove singularity lies even closer to the Fermi level in NiTe2 than in PdTe2. To explain the lack of superconductivity in NiTe2, we perform ab initio calculations incorporating the Kukkonen Overhauser interaction, showing that an incipient magnetic instability suppresses superconductivity at an unprecedented scale. Finally, we present a tight-binding model that links the Van Hove singularity to a sign change in the Josephson diode effect at small magnetic fields, suggesting a new mechanism for Josephson diodes.
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Feb 2026
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B16-Test Beamline
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S.-X.
Wang
,
Z.-Q.
Zhao
,
X.-Y.
Wang
,
T.-J.
Li
,
Y.
Su
,
Y.
Uemura
,
F.
Alves Lima
,
A.
Khadiev
,
B.-H.
Wang
,
J. M.
Ablett
,
J.-P.
Rueff
,
H.-C.
Wang
,
O. J. L.
Fox
,
Wenbin
Li
,
L.-F.
Zhu
,
X.-C.
Huang
Diamond Proposal Number(s):
[31397]
Open Access
Abstract: X-ray cavity quantum optics with inner-shell transitions has been limited by the spectral overlap between resonant and continuum states. Here, we report the first experimental demonstration of cavity-controlled core-to-core resonant inelastic x-ray scattering (RIXS). We suppress the absorption-edge effects by monitoring the RIXS profile, thereby resolving the resonant state from the overlapping continuum. We observe distinct cavity-induced energy shifts and cavity-enhanced decay rates in the 2𝑝3𝑑 RIXS spectra of WSi2. These effects, manifesting as stretched or shifted profiles in the RIXS planes, enable novel spectroscopic applications via cavity-controlled core-hole states. Our results establish core-to-core RIXS as a powerful tool to manipulate inner-shell dynamics in x-ray cavities, offering new avenues for integrating quantum optical effects with x-ray spectroscopy.
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Feb 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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D.
Takegami
,
T.
Aoyama
,
T.
Okauchi
,
T.
Yamaguchi
,
S.
Tippireddy
,
S.
Agrestini
,
Mirian
Garcia-Fernandez
,
T.
Mizokawa
,
K.
Ohgushi
,
Ke-Jin
Zhou
,
J.
Chaloupka
,
J.
Kuneš
,
A.
Hariki
,
H.
Suzuki
Diamond Proposal Number(s):
[35709]
Open Access
Abstract: X-ray magnetic circular dichroism provides a means to identify ferromagnetic, chiral, and altermagnetic orders via their time-reversal-symmetry (𝒯) breaking. However, the symmetry properties that govern circular dichroism (CD) in resonant inelastic x-ray scattering (RIXS) remain poorly understood. We show that, due to the inherent irreversibility of the RIXS process, RIXS-CD does not require 𝒯 breaking to be present, but reflects the change in unitary symmetries associated with magnetic ordering. Using the altermagnetic MnTe as a model system, we observe an azimuthal-angle dependent RIXS-CD signal in the magnon excitations. Our findings highlight the sensitivity of RIXS-CD to the relativistic symmetry in magnetic systems and its potential application as a probe of magnetic domains.
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Nov 2025
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I09-Surface and Interface Structural Analysis
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C.-H.
Min
,
M.
Scholz
,
T.-L.
Lee
,
C.
Schlueter
,
A.
Gloskovskii
,
E. D. L.
Rienks
,
V.
Hinkov
,
H.
Bentmann
,
Y. S.
Kwon
,
F.
Reinert
,
H.-D.
Kim
,
K.
Rossnagel
,
S.
Müller
,
W. J.
Choi
,
V.
Zabolotnyy
,
M.
Heber
,
J. D.
Denlinger
,
C.-J.
Kang
,
M.
Kalläne
,
N.
Wind
,
L.
Dudy
Diamond Proposal Number(s):
[22630]
Abstract: Exotic quasiparticle states have been proposed in mixed-valent compounds exhibiting valence transitions. However, clear spectroscopic evidence identifying these states has remained elusive. Using synchrotron-based hard x-ray and extreme ultraviolet photoemission spectroscopy, we have probed the Tm 3𝑑 and 4𝑓 emissions in TmSe1−𝑥Te𝑥, where a Te concentration-dependent semimetal–insulator transition occurs alongside the valence transition. Our photoemission results, which are characteristic of the bulk, track this combined transition across the critical concentration (𝑥𝑐 =0.29). Notably, our results reveal a noninteger valence for the insulating phase and a novel quasiparticle excitation in the semimetallic phase: a Holstein polaron that extends beyond the standard periodic Anderson model.
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Oct 2025
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[35227]
Open Access
Abstract: Electron spin resonance can provide unique insights into charge transport processes in organic semiconductors in a regime in which charge motion determines spin relaxation. In particular, electrically detected magnetic resonance (EDMR) probes directly the changes in charge transport properties that are sensitive to magnetic resonance excitation. Here, we present a systematic study of continuous-wave EDMR on conjugated polymer field-effect transistors (FETs) that can be operated in both unipolar as well as ambipolar regimes. We show that, in addition to a narrow, electron-hole recombination-induced EDMR signal that can only be detected in the ambipolar regime, there is also a broad EDMR signal when devices are operated in both unipolar and ambipolar regions. We attribute this signal to a spin blockade mechanism induced when mobile carriers encounter trapped charges along the charge transport percolation pathways and study its dependence on biasing conditions and temperature. The spin-blockade EDMR signature is also observed in conjugated polymer FETs that exhibit only unipolar operation. Our findings show that EDMR provides a powerful technique to study the role of spin blockade and bipolaron formation on the charge transport properties of a wide range of conjugated polymers.
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Oct 2025
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I15-1-X-ray Pair Distribution Function (XPDF)
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Ming
Gao
,
Hankun
Xu
,
Kun
Lin
,
Andrea
Sanson
,
Alessandro
Venier
,
Alessandro
Puri
,
Jochi
Tseng
,
Guodong
Li
,
Qian
Zhang
,
Xuyu
Dong
,
Yili
Cao
,
Qiang
Li
,
Xianran
Xing
Diamond Proposal Number(s):
[31899]
Abstract: Negative thermal expansion (NTE) is an unusual yet highly useful phenomenon that has been extensively studied in numerous crystals, including ceramics, alloys, and metal-organic frameworks. This Letter reports an unprecedented NTE in an amorphous Fe87.5Y3Zr1.5B8 alloy that lacks a periodic atomic arrangement. Such an NTE is significant for metallic materials and extends over a wide temperature range (𝛼1=−6.9×10−6 K−1, 200–375 K). We demonstrate that this NTE is intrinsic to the amorphous nature of the alloy and is correlated with Fe moment. Extended x-ray absorption fine structure reveals a strong NTE for nearest neighboring Fe-Fe pairs. Further analysis using a x-ray pair distribution function indicates that the amorphous Fe87.5Y3Zr1.5B8 alloy, serving as a transition state, exhibits a tendency toward local ordered atomic arrangement. A complex interplay among local structure, magnetic interaction, and thermal relaxation results in volume contraction upon heating below 𝑇𝐶. This Letter introduces amorphous alloys as a new family of materials with NTE functionality, offering interesting prospects for both scientific research and practical applications.
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Sep 2025
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I10-Beamline for Advanced Dichroism - scattering
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Miming
Cai
,
Shangyuan
Wang
,
Yuelin
Zhang
,
Xiaoqing
Bao
,
Dekun
Shen
,
Jinghua
Ren
,
Lei
Qiu
,
Haiming
Yu
,
Zhenlin
Luo
,
Mathias
Kläui
,
Shilei
Zhang
,
Nicolas
Jaouen
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Ka
Shen
,
Jinxing
Zhang
Diamond Proposal Number(s):
[36632]
Abstract: Symmetry engineering is an effective approach for generating emergent phases and quantum phenomena. In magnetic systems, the Dzyaloshinskii-Moriya (DM) interaction is essential for stabilizing chiral spin textures. The symmetry manipulation of DM vectors, described in three dimensions, could provide a strategy toward creating abundant topologically magnetic phases. Here, we have achieved breaking the rotational and mirror symmetries of the three-dimensional DM vectors in a strongly correlated ferromagnet, which were directly measured through the nonreciprocal spin-wave propagations in both in-plane and out-of-plane magnetic field geometries. Combining cryogenic magnetic force microscopy and micromagnetic simulations, we discover a bimeron phase that emerges between the spin spiral and skyrmion phases under an applied magnetic field. Such an artificially manipulated DM interaction is shown to play a critical role in the formation and evolution of the large-area bimeron lattice, a phenomenon that could be realized across a broad range of materials. Our findings demonstrate that symmetry engineering of the DM vectors can be practically achieved through epitaxial strain, paving the way for the creation of diverse spin topologies and the exploration of their emergent functionalities.
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Sep 2025
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I16-Materials and Magnetism
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Diamond Proposal Number(s):
[20056]
Open Access
Abstract: The unabating discovery of nanoskyrmions in centrosymmetric magnets challenges the conventional Dzyaloshinskii-Moriya (DM) skyrmion stabilization mechanism. We investigate Gd2PdSi3 using polarized resonant x-ray scattering and find that the low-field incommensurate modulations are elliptical helices, evolving into spin-density waves at higher fields. Quasi-2D magnetism arises via local DM interactions generated by inversion symmetry breaking around Gd-Gd bonds, which we characterize using atomistic simulations. Our findings suggest a prominent “hidden” role of DM interactions even in centrosymmetric skyrmionic hosts.
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Aug 2025
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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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