I05-ARPES
|
Chakradhar
Sahoo
,
Suman Kumar
Chakraborty
,
Anbalagan
Kousika
,
Alfred J. H.
Jones
,
Manas
Sharma
,
Thomas S.
Nielsen
,
Zhihao
Jiang
,
Ihsan A.
Kolasseri
,
Subhadip
Das
,
Matthew D.
Watson
,
Cephise
Cacho
,
Kenji
Watanabe
,
Takashi
Taniguchi
,
Yong P.
Chen
,
Tony F.
Heinz
,
Ananth
Govind Rajan
,
Prasana K.
Sahoo
,
Søren
Ulstrup
Diamond Proposal Number(s):
[36290, 38414]
Abstract: Atomic-scale control over band alignment in single-layer lateral heterostructures (LHSs) of dissimilar transition metal dichalcogenides (TMDCs) is critical for next-generation electronic, optoelectronic, and quantum technologies. However, direct experimental access to interfacial electronic states with nanometer precision remains a significant challenge. Here, we employ angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES) to directly map the epitaxial alignment and valence band evolution across the MoSe2–WSe2 LHSs. By combining nanoARPES with spatially resolved photoluminescence, we correlate the evolution of the valence band maximum and exciton features across both atomically sharp and compositionally graded diffusive interfaces. We identified type-II band alignments governed by both material composition and interstitial-induced modifications of band offsets in close agreement with density functional theory calculations. These results reveal fundamental mechanisms of electronic structure modulation at 1D TMDC heterointerfaces and provide a robust platform for tailored band engineering in van der Waals materials.
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Apr 2026
|
|
I05-ARPES
|
Aymeric
Saunot
,
Vesna
Mikšić Trontl
,
Ilya I.
Klimovskikh
,
Denis V.
Vyalikh
,
Alex
Louat
,
Cephise
Cacho
,
Asish K.
Kundu
,
Elio
Vescovo
,
Ivana
Vobornik
,
Alexander
Fedorov
,
Cedomir
Petrovic
,
Tonica
Valla
Diamond Proposal Number(s):
[36637]
Abstract: CeTe3 is a 2-dimensional (2D) Van der Waals (VdW) material with incommensurate charge density waves (CDW), extremely high transition temperature ( ), and a large momentum-dependent CDW gap that leaves a significant portion of the Fermi surface intact. It is also considered to be a weak Kondo system, a property unexpected for a material with incommensurate CDW, where each atomic site is slightly different. Here, we study the properties of the CDW state in several RTe3 (R is rare earth) materials and examine the hybridization of itinerant states with the localized Ce 4f multiplet in CeTe3 by using angle resolved photoemission spectroscopy. We find that the renormalization of the itinerant states originating from the hybridization with the deeper localized 4f states at meV is dependent and extends to the Fermi level. As these localized states are far from the Fermi level, the observed hybridization affects the effective masses only marginally and does not lead to heavy fermions. However, since the same renormalizing mechanism normally leads to the heavy fermion physics when the localized 4f states are near the Fermi level, our observation of its strong dependence suggests that this could be the reason for discrepancy between the heavy masses in specific heat and light ones in Shubnikov de Haas oscillations, often observed in heavy fermions.
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Mar 2026
|
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I05-ARPES
|
Yuval
Nitzav
,
Roni A.
Kiassi Gofman
,
Ilay
Mangel
,
Abigail
Dishi
,
Nitzan
Ragoler
,
K. P.
Sajilesh
,
Yaron
Jarach
,
Alex
Louat
,
Matthew D.
Watson
,
Cephise
Cacho
,
Irena
Feldman
,
Amit
Kanigel
Diamond Proposal Number(s):
[33131]
Abstract: The origin of the insulating state in 1𝑇 −TaS2 has long been a subject of debate. A short current pulse transforms this insulating state into a metastable metallic phase. Using micro–angle-resolved photoemission spectroscopy, we investigate the electronic structure of this phase and uncover spatially dependent modifications caused by the current pulse. In some regions of the sample, a Fermi surface emerges, while others remain gapped. Detailed band structure analysis reveals that the metallic regions exhibit an electronic structure similar to that observed in the high-temperature phase of 1𝑇 −TaS2, characterized by suppressed energy gaps and bands crossing the Fermi level. Furthermore, the metallic and insulating regions display distinct out of plane dispersions, consistent with the current pulse influencing the Star of David dimers that characterize the insulating phase.
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Feb 2026
|
|
E02-JEM ARM 300CF
I05-ARPES
|
Amy
Carl
,
Nicholas
Clark
,
David G.
Hopkinson
,
Matthew
Hamer
,
Matthew
Watson
,
Laxman
Nagireddy
,
James E.
Nunn
,
Alexei
Barinov
,
Yichao
Zou
,
William
Thornley
,
Casey
Cheung
,
Wendong
Wang
,
Sam
Sullivan-Allsop
,
Xiao
Li
,
Astrid
Weston
,
Eli G.
Castanon
,
Andrey V.
Kretinin
,
Cephise
Cacho
,
Neil R.
Wilson
,
Sarah J.
Haigh
,
Roman
Gorbachev
Diamond Proposal Number(s):
[21597, 21981, 24290, 24338]
Open Access
Abstract: Magnetic two-dimensional materials are a promising platform for novel nano-electronic device architectures. One such layered crystal is the ferromagnetic semiconductor chromium germanium telluride (Cr2Ge2Te6) which recently attracted interest due to its potential for spintronics and memory applications. Here we investigate its properties from the structural standpoint using atomic resolution Scanning Transmission Electron Microscopy (STEM) and present the first atomic resolution images down to its monolayer limit. We develop a novel technique that allows one to map the local tilt with unprecedented spatial resolution using only high-resolution images, enabling mapping of the topography and morphological variation of atomically thin crystals. Using it, we show that the Cr2Ge2Te6 monolayer has an unusually large out-of-plane rippling, with local tilt variation reaching 20° over few nm length scales. We hypothesize that such a strongly buckled structure originates from both point and extended lattice defects which are more prevalent in monolayer crystals. In addition, we correlate the structural observations with the band structure measurements using Angle-Resolved Photoemission Spectroscopy (ARPES). We believe that both the atomic scale insights we have gained on Cr2Ge2Te6 and our novel approach to nanoscale topography mapping will benefit the development of van der Waals heterostructures in both fundamental and applied research.
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Feb 2026
|
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I05-ARPES
|
Diamond Proposal Number(s):
[37658, 36215, 39549]
Open Access
Abstract: We report the electronic structure of monolayer CrSBr exfoliated onto mica template-stripped gold substrates. Angle-resolved photoemission spectroscopy reveals charge transfer from the substrate, populating the conduction band of monolayer CrSBr, accompanied by a pronounced reduction in the quasiparticle band gap. Furthermore, we observe two separate conduction bands that exhibit a splitting at the X point. This indicates a breaking of glide-mirror symmetry, which in the bulk or in a free-standing monolayer protects the band degeneracies at the Brillouin zone boundary. Our results demonstrate that ultraflat gold substrates do more than modify carrier densities and screening: they can lift symmetry-protected degeneracies and thus fundamentally reshape the band topology of 2D materials.
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Jan 2026
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I05-ARPES
|
Songyuan
Geng
,
Xin
Wang
,
Risi
Guo
,
Chen
Qiu
,
Fangjie
Chen
,
Qun
Wang
,
Kangjie
Li
,
Peipei
Hao
,
Hanpu
Liang
,
Yang
Huang
,
Yunbo
Wu
,
Shengtao
Cui
,
Zhe
Sun
,
Timur K.
Kim
,
Cephise
Cacho
,
Daniel S.
Dessau
,
Benjamin T.
Zhou
,
Haoxiang
Li
Diamond Proposal Number(s):
[38254]
Open Access
Abstract: Flat electronic bands, where interactions among electrons overwhelm their kinetic energies, hold the promise for exotic correlation physics. The dice lattice has long been theorized as a host of flat bands with intriguing band topology. However, to date, no material has ever been found to host the characteristic flat bands of a dice lattice. Here, using angle-resolved photoemission spectroscopy (ARPES), we discover a dice-lattice flat band at EF in the van der Waals (vdW) electride [YCl]2+: 2e-. In this system, excess valence electrons from Y deconfine from the cation framework to form an interstitial anionic electron lattice that constitutes the dice lattice. Our ARPES measurements unambiguously identify two sets of dice-lattice bands in YCl, including a nearly dispersionless band at the Fermi level. The near-EF electronic structure observed in ARPES, which consists of the flat bands and other dispersive band features, find excellent agreement with first-principles calculations and is well captured by a simple dice-lattice model. Our findings thus end the long quest of a real dice flat band material and establish vdW electride YCl as a prototype of dice metals. Our results further demonstrate the anionic electron lattice as a novel scheme for realizing lattice geometries and electronic structures rare to find in conventional crystalline systems.
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Jan 2026
|
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I05-ARPES
|
I.
Biało
,
Qisi
Wang
,
J.
Küspert
,
X.
Hong
,
L.
Martinelli
,
O.
Gerguri
,
Y.
Chan
,
K.
Von Arx
,
O. K.
Forslund
,
W. R.
Pudełko
,
C.
Lin
,
N. C.
Plumb
,
Y.
Sassa
,
D.
Betto
,
N. B.
Brookes
,
M.
Rosmus
,
N.
Olszowska
,
Ma. D.
Watson
,
T. K.
Kim
,
C.
Cacho
,
M.
Horio
,
M.
Ishikado
,
H. M.
Rønnow
,
J.
Chang
Diamond Proposal Number(s):
[32147]
Open Access
Abstract: Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of these interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compounds with the highest superconducting onset temperature. To fill this gap, we introduce a pristine, half-filled thallium-based cuprate system, Tl2Ba5Cu4Ox. Using high-resolution resonant inelastic x-ray scattering, we probe long-lived magnon excitations and uncover a pronounced kink in the magnon dispersion, marked by a simultaneous change in group velocity and lifetime broadening. Modeling the dispersion within a Hubbard-Heisenberg approach, we extract the interaction strength and compare it with other cuprate systems. Our results establish a cuprate universal relation between electron-electron interaction and magnon zone-boundary dispersion. Superconductivity seems to be optimal at intermediate correlation strength, suggesting an optimal balance between localization and itinerancy.
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Dec 2025
|
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I05-ARPES
|
Diamond Proposal Number(s):
[34479, 33317, 35210]
Open Access
Abstract: Understanding the interface between metals and two-dimensional materials is critical for their application in electronics and for the development of metal-mediated exfoliation of large area monolayers. Studying the intricate interactions at the interface requires model systems that enable control of the roughness, purity, and crystallinity of the metal surface. Here, we use angle-resolved photoemission spectroscopy to investigate the layer-dependent electronic structure of WSe\textsubscript{2}~on template-stripped gold substrates fabricated using both silicon and mica templates, giving crystallographically disordered and Au(111) ordered surfaces, respectively, and contrast these findings with \textit{ab initio} predictions. We observe strong hybridization around the Brillouin zone centre at $\overline{\Gamma}$, indicating a covalent admixture in the gold-WSe\textsubscript{2}~interaction, and band shifts that suggest charge rearrangement at the Au(111) / WSe\textsubscript{2}~interface. Core-level spectroscopy shows a single chemical environment for the interfacial WSe\textsubscript{2}~layer on the template-stripped gold, distinct from the subsequent layers. These results reveal a mixture of van der Waals and covalent interactions, best described as a covalent-like quasi-bonding with intermediate interaction strength.
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Oct 2025
|
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I05-ARPES
|
Zhisheng
Zhao
,
Tongrui
Li
,
Peng
Li
,
Xueliang
Wu
,
Jianghao
Yao
,
Ziyuan
Chen
,
Yajun
Yan
,
Shengtao
Cui
,
Zhe
Sun
,
Yichen
Yang
,
Zhicheng
Jiang
,
Zhengtai
Liu
,
Alex
Louat
,
Timur
Kim
,
Cephise
Cacho
,
Aifeng
Wang
,
Yilin
Wang
,
Dawei
Shen
,
Juan
Jiang
,
Donglai
Feng
Diamond Proposal Number(s):
[32274]
Abstract: The kagome metal FeGe provides a rich platform for understanding the mechanisms behind competing orders, as it exhibits charge order (CO) emerging deep within the antiferromagnetic phase. To investigate the intrinsic origin of this behavior, we examine the evolution of the low-energy electronic structure across the phase transition in annealed FeGe samples using angle-resolved photoemission spectroscopy. We find no evidence supporting a conventional nesting mechanism, such as Fermi surface nesting or van Hove singularities. However, we observe two notable changes in the band structure: an electron-like band around the K point and another around the A point, both shifting upward in energy when CO forms. These findings are consistent with our density-functional theory calculations, which suggest that the charge order in FeGe is primarily driven by magnetic energy savings due to a lattice distortion involving Ge1-dimerization. Our results provide photoemission evidence supporting this novel mechanism for CO formation in FeGe, in contrast to the conventional nesting-driven mechanisms.
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Jun 2025
|
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I05-ARPES
|
Steef
Smit
,
Kourosh L.
Shirkoohi
,
Saumya
Mukherjee
,
Sergio Barquero
Pierantoni
,
Lewis
Bawden
,
Erik
Van Heumen
,
Arnaud Pastel Nono
Tchiomo
,
Jans
Henke
,
Jasper
Van Wezel
,
Yingkai
Huang
,
Takeshi
Kondo
,
Tsunehiro
Takeuchi
,
Timur K.
Kim
,
Cephise
Cacho
,
Marta
Zonno
,
Sergey
Gorovikov
,
Stephen B.
Dugdale
,
Jorge I.
Facio
,
Mariia
Roslova
,
Laura
Folkers
,
Anna
Isaeva
,
Nigel
Hussey
,
Mark
Golden
Diamond Proposal Number(s):
[19403, 22464]
Open Access
Abstract: High-resolution angle-resolved photoemission spectroscopy (ARPES) performed on the single-layered cuprate (Pb
1
−
y
,Bi
y
)
2
Sr
2
−
x
La
x
CuO
6
+
δ
(Bi2201) reveals a 6-10% difference in the nodal
k
F
vectors along the
Γ
Y and
Γ
X directions. This asymmetry is notably larger than the 2% orthorhombic distortion in the CuO
2
plane lattice constants determined using X-ray crystallography from the same samples. First principles calculations indicate that crystal-field splitting of the bands lies at the root of the
k
F
asymmetry. Concomitantly, the nodal Fermi velocities for the
Γ
Y quadrant exceed those for
Γ
X by 4%. Momentum distribution curve widths for the two nodal dispersions are also anisotropic, showing identical energy dependencies, bar a scaling factor of
∼
1.17
±
0.05
between
Γ
Y and
Γ
X. Consequently, the imaginary part of the self-energy is found to be 10-20% greater along
Γ
Y than
Γ
X. These results emphasize the need to account for Fermi surface asymmetry in the analysis of ARPES data on Bi-based cuprate high temperature superconductors such as Bi2201. To illustrate this point, an orthorhombic tight-binding model (with twofold in-plane symmetry) was used to fit ARPES Fermi surface maps spanning all four quadrants of the Brillouin zone, and the ARPES-derived hole-doping (Luttinger count) was extracted. Comparison of the Luttinger count with one assuming four-fold in-plane symmetry strongly suggests the marked spread in previously-reported Fermi surface areas from ARPES on Bi2201 results from the differences in
k
F
along
Γ
Y and
Γ
X. Using this analysis, a new, linear relationship emerges between the hole-doping derived from ARPES (
p
ARPES
) and that derived using the Presland (
p
Presland
) relation such that
p
ARPES
=
p
Presland
+
0.11
. The implications for this difference between the ARPES- and Presland-derived estimates for
p
are discussed and possible future directions to elucidate the origin of this discrepancy are presented.
|
Jun 2025
|
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