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141 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I10-Beamline for Advanced Dichroism - scattering	Slow equilibrium relaxation in a chiral magnet mediated by topological defects Chenhao Zhang , Yang Wu , Jingyi Chen , Haonan Jin , Jinghui Wang , Raymond Fan , Paul Steadman , Gerrit Van Der Laan , Thorsten Hesjedal , Shilei Zhang Physical Review Letters 133 DOI: 10.1103/PhysRevLett.133.166707 Diamond Proposal Number(s): [34423, 34827] Show Abstract ▼ Abstract: We performed a pump-probe experiment on the chiral magnet Cu2⁢OSeO3 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.	Oct 2024
I21-Resonant Inelastic X-ray Scattering (RIXS)	Origin of magnetism in a supposedly nonmagnetic osmium oxide 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 Physical Review Letters 133 DOI: 10.1103/PhysRevLett.133.066501 Open Access Show Abstract ▼ Abstract: A supposedly nonmagnetic 5⁢𝑑1 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 5⁢𝑑 𝑡2⁢𝑔 and 𝑒𝑔 orbitals, covalency raises the 5⁢𝑑 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 5⁢𝑑1 ions. Our results provide direct evidence of elusive Jahn-Teller distortions, hinting at a strong electron-lattice coupling.	Aug 2024
I05-ARPES	Fermi surface nesting driving the RKKY interaction in the centrosymmetric skyrmion magnet Gd2PdSi3 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 Physical Review Letters 133 DOI: 10.1103/PhysRevLett.133.016401 Diamond Proposal Number(s): [30646, 28930, 25416] Show Abstract ▼ Abstract: The magnetic skyrmions generated in a centrosymmetric crystal were recently first discovered in Gd2⁢PdSi3. 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 Gd2⁢PdSi3.	Jul 2024
I09-Surface and Interface Structural Analysis	Structure of graphene grown on Cu(111): X-ray standing wave measurement and density functional theory prediction Matthew A. Stoodley , Luke A. Rochford , Tien-Lin Lee , Benedikt P. Klein , David A. Duncan , Reinhard J. Maurer Physical Review Letters 132 DOI: 10.1103/PhysRevLett.132.196201 Diamond Proposal Number(s): [25379] Open Access Show Abstract ▼ Abstract: We report the quantitative adsorption structure of pristine graphene on Cu(111) determined using the normal incidence x-ray standing wave technique. The experiments constitute an important benchmark reference for the development of density functional theory approximations able to capture long-range dispersion interactions. Electronic structure calculations based on many-body dispersion-inclusive density functional theory are able to accurately predict the absolute measure and variation of adsorption height when the coexistence of multiple moiré superstructures is considered. This provides a structural model consistent with scanning probe microscopy results.	May 2024
I05-ARPES	Bias-free access to orbital angular momentum in two-dimensional quantum materials 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 Physical Review Letters 132 DOI: 10.1103/PhysRevLett.132.196401 Diamond Proposal Number(s): [30583] Show Abstract ▼ 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.	May 2024
I06-Nanoscience (XPEEM)	X-ray magnetic circular dichroism in altermagnetic α-MnTe A. Hariki , A. Dal Din , O. j. Amin , T. Yamaguchi , A. Badura , D. Kriegner , K. W. Edmonds , R. p. Campion , P. Wadley , D. Backes , L. S. I. Veiga , S. S. Dhesi , G. Springholz , L. Šmejkal , K. Výborný , T. Jungwirth , J. Kuneš Physical Review Letters 132 DOI: 10.1103/PhysRevLett.132.176701 Diamond Proposal Number(s): [33456, 36317] Show Abstract ▼ Abstract: Altermagnetism is a recently identified magnetic symmetry class combining characteristics of conventional collinear ferromagnets and antiferromagnets, that were regarded as mutually exclusive, and enabling phenomena and functionalities unparalleled in either of the two traditional elementary magnetic classes. In this work we use symmetry, ab initio theory, and experiments to explore x-ray magnetic circular dichroism (XMCD) in the altermagnetic class. As a representative material for our XMCD study we choose α -MnTe with compensated antiparallel magnetic order in which an anomalous Hall effect has been already demonstrated. We predict and experimentally confirm a characteristic XMCD line shape for compensated moments lying in a plane perpendicular to the light propagation vector. Our results highlight the distinct phenomenology in altermagnets of this time-reversal symmetry breaking response, and its potential utility for element-specific spectroscopy and microscopy.	Apr 2024
I21-Resonant Inelastic X-ray Scattering (RIXS)	Evolution of the magnetic excitations in electron-doped La2−xCexCuO4 X. T. Li , S. J. Tu , L. Chaix , C. Fawaz , M. D’astuto , X. Li , F. Yakhou-Harris , K. Kummer , N. B. Brookes , Mirian Garcia-Fernandez , K.-J. Zhou , Z. F. Lin , J. Yuan , K. Jin , M. P. Dean , X. Liu Physical Review Letters 132 DOI: 10.1103/PhysRevLett.132.056002 Diamond Proposal Number(s): [27478] Show Abstract ▼ Abstract: We investigated the high energy spin excitations in electron-doped La 2 − x Ce x CuO 4 , a cuprate superconductor, by resonant inelastic x-ray scattering (RIXS) measurements. Efforts were paid to disentangle the paramagnon signal from non-spin-flip spectral weight mixing in the RIXS spectrum at Q ∥ = ( 0.6 π , 0 ) and ( 0.9 π , 0 ) along the (1 0) direction. Our results show that, for doping level x from 0.07 to 0.185, the variation of the paramagnon excitation energy is marginal. We discuss the implication of our results in connection with the evolution of the electron correlation strength in this system.	Feb 2024
I21-Resonant Inelastic X-ray Scattering (RIXS)	Collective nature of orbital excitations in layered cuprates in the absence of apical oxygens Leonardo Martinelli , Krzysztof Wohlfeld , Jonathan Pelliciari , Riccardo Arpaia , Nicholas B. Brookes , Daniele Di Castro , Mirian Garcia-Fernandez , Mingu Kang , Yoshiharu Krockenberger , Kurt Kummer , Daniel E. Mcnally , Eugenio Paris , Thorsten Schmitt , Hideki Yamamoto , Andrew Walters , Ke-Jin Zhou , Lucio Braicovich , Riccardo Comin , Marco Moretti Sala , Thomas P. Devereaux , Maria Daghofer , Giacomo Ghiringhelli Physical Review Letters 132 DOI: 10.1103/PhysRevLett.132.066004 Diamond Proposal Number(s): [20690] Show Abstract ▼ Abstract: We have investigated the 3 d orbital excitations in CaCuO 2 (CCO), Nd 2 CuO 4 (NCO), and La 2 CuO 4 (LCO) using high-resolution resonant inelastic x-ray scattering. In LCO they behave as well-localized excitations, similarly to several other cuprates. On the contrary, in CCO and NCO the d x y orbital clearly disperses, pointing to a collective character of this excitation (orbiton) in compounds without apical oxygen. We ascribe the origin of the dispersion as stemming from a substantial next-nearest-neighbor (NNN) orbital superexchange. Such an exchange leads to the liberation of the orbiton from its coupling to magnons, which is associated with the orbiton hopping between nearest neighbor copper sites. Finally, we show that the exceptionally large NNN orbital superexchange can be traced back to the absence of apical oxygens suppressing the charge transfer energy.	Feb 2024
I05-ARPES	Fate of quasiparticles at high temperature in the correlated metal Sr2RuO4 A. Hunter , S. Beck , E. Cappelli , F. Margot , M. Straub , Y. Alexanian , G. Gatti , M. D. Watson , T. K. Kim , C. Cacho , N. cc. Plumb , M. Shi , M. Radović , D. A. Sokolov , A. p. Mackenzie , M. Zingl , J. Mravlje , A. Georges , F. Baumberger , A. Tamai Physical Review Letters 131 DOI: 10.1103/PhysRevLett.131.236502 Diamond Proposal Number(s): [25083] Show Abstract ▼ Abstract: We study the temperature evolution of quasiparticles in the correlated metal Sr 2 RuO 4 . Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200 K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy, we demonstrate that the quasiparticle residue Z increases with increasing temperature. Quasiparticles eventually disappear on approaching the bad metal state of Sr 2 RuO 4 not by losing weight but via excessive broadening from super-Planckian scattering. We further show that the Fermi surface of Sr 2 RuO 4 —defined as the loci where the spectral function peaks—deflates with increasing temperature. These findings are in semiquantitative agreement with dynamical mean field theory calculations.	Dec 2023
I05-ARPES	Flat Γ Moiré bands in twisted bilayer WSe2 G. Gatti , J. Issing , L. Rademaker , F. Margot , T. A. De Jong , S. J. Van Der Molen , J. Teyssier , T. K. Kim , M. D. Watson , C. Cacho , P. Dudin , J. Avila , K. Cordero-Edwards , P. Paruch , N. Ubrig , I. Gutiérrez-Lezama , A. f. Morpurgo , A. Tamai , F. Baumberger Physical Review Letters 131 DOI: 10.1103/PhysRevLett.131.046401 Diamond Proposal Number(s): [29021] Show Abstract ▼ Abstract: The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moiré superlattice effects in 57.4° twisted WSe 2 ( tWSe 2 ). Our data reveal a split-off flat band that derives from the monolayer Γ states. Using advanced data analysis, we directly quantify the moiré potential from our data. We further demonstrate that the global valence band maximum in tWSe 2 is close in energy to this flat band but derives from the monolayer K states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that Γ -valley flat bands might be involved in the correlated physics of twisted WSe 2 .	Jul 2023

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