I05-ARPES
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Xingtian
Sun
,
Suppanut
Sangphet
,
Nan
Guo
,
Yu
Fan
,
Yutong
Chen
,
Minyinan
Lei
,
Xue
Ming
,
Xiyu
Zhu
,
Hai-Hu
Wen
,
Haichao
Xu
,
Rui
Peng
,
Donglai
Feng
Diamond Proposal Number(s):
[39544]
Abstract: The superconducting transition temperatures (𝑇c’s) of trilayer or quadruple-layer cuprates typically surpass those of single-layer or bilayer systems. However, the lack of direct electronic-structure and superconducting-gap measurements in optimal-𝑇c quadruple-layer cuprates has impeded a comprehensive understanding of the origin of the enhanced 𝑇c in multilayer systems. In this Letter, using angle-resolved photoemission spectroscopy, we investigate the quadruple-layer cuprate (Cu,C)Ba2Ca3Cu4O11+𝛿 (CuC-1234) with a high 𝑇c of 110 K, and resolved distinct superconducting-gap behaviors between the inner CuO2 planes and outer CuO2 planes, in contrast to that reported for trilayer cuprates. Outer CuO2 planes develop their own superconducting gap and superconducting coherence peak at a temperature much lower than the 𝑇c of the material, while the large pairing strength and phase coherence concurrently emerge at the underdoped inner CuO2 planes at 𝑇c. Our findings suggest that CuO2 planes free of apical oxygen can have significant contribution to superconductivity up to 110 K in multilayer cuprates, even at a doping level of 0.07 holes per Cu, a level that lies deep in the underdoped regime of single- and bilayer cuprates. These findings provide new insights into the origin of high 𝑇c in multilayer cuprates.
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May 2026
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I05-ARPES
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Xian
Yang
,
Chia-Hsiu
Hsu
,
Gokul
Acharya
,
Junyi
Zhang
,
Md shafayat
Hossain
,
Tyler A.
Cochran
,
Bimal
Neupane
,
Zi-Jia
Cheng
,
Santosh Karki
Chhetri
,
Byunghoon
Kim
,
Shiyuan
Gao
,
Yu-Xiao
Jiang
,
Maksim
Litskevich
,
Jian
Wang
,
Yuanxi
Wang
,
Jin
Hu
,
M. Zahid
Hasan
Abstract: Topological materials hold immense promise for exhibiting exotic quantum phenomena, yet achieving controllable topological phase transitions remains challenging. Here, we demonstrate a structurally driven, reversible topological phase transition in the distorted square net material GdPS, induced via in situ potassium dosing. Using angle-resolved photoemission spectroscopy and first principles calculations, we demonstrate a cascade of topological phases in the subsurface P layer: from a large, topologically trivial band gap to a gapless Dirac cone state with a 2 eV dispersion, and finally to a two-dimensional topological insulator as inferred from theory. This evolution is driven by subtle structural distortions in the first P layer caused by potassium adsorption, which in turn contribute to the band gap closure and topological phase transition. Furthermore, the ability to manipulate the topology of a subsurface layer in GdPS offers a unique route for exploring and controlling topological states in bulk materials.
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Mar 2026
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[39378]
Open Access
Abstract: We discover a rare structural manifestation of the Goldstone paradigm in a hexagonal polytype of the prototypical ferroelectric BaTiO3. First-principles calculations confirm the Goldstone character of the order parameter, while our high-resolution diffraction measurements unveil an unusual reentrant Goldstone regime manifesting as a quasicontinuous domain texture in the vicinity of the ferroelectric transition. We develop a minimal Landau model that encapsulates these observations, illustrating how U(1) symmetry can be restored at the ferroelectric transition. Our findings demonstrate how exotic Goldstone physics can be unlocked in systems dominated by highly anharmonic interactions, presenting a promising pathway to stabilize emergent polar topologies in bulk materials.
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Mar 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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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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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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