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129 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
I09-Surface and Interface Structural Analysis	Atomic-site-specific surface valence-band structure from X-ray standing-wave excited photoemission Yanna Chen , Leighton O. Jones , Tien-Lin Lee , Anusheela Das , Martín A. Mosquera , Denis T. Keane , George C. Schatz , Michael J. Bedzyk Physical Review Letters 128 DOI: 10.1103/PhysRevLett.128.206801 Diamond Proposal Number(s): [20076] Show Abstract ▼ Abstract: X-ray standing-wave (XSW) excited photoelectron emission was used to measure the site-specific valence band (VB) for ½ monolayer (ML) Pt grown on a SrTiO 3 (001) surface. The XSW induced modulations in the core level (CL), and VB photoemission from the surface and substrate atoms were monitored for three h k l substrate Bragg reflections. The XSW CL analysis shows the Pt to have a face-centered-cubic-like cube-on-cube epitaxy with the substrate. The XSW VB information compares well to a density functional theory calculated projected density of states from the surface and substrate atoms. Overall, this Letter represents a novel method for determining the contribution to the density of states by valence electrons from specific atomic surface sites.	May 2022
	Hidden k-space magnetoelectric multipoles in nonmagnetic ferroelectrics Sayantika Bhowal , Stephen P. Collins , Nicola A. Spaldin Physical Review Letters 128 DOI: 10.1103/PhysRevLett.128.116402 Open Access Show Abstract ▼ Abstract: In condensed matter systems, the electronic degrees of freedom are often entangled to form complex composites, known as hidden orders, which give rise to unusual properties, while escaping detection in conventional experiments. Here we demonstrate the existence of hidden k -space magnetoelectric multipoles in nonmagnetic systems with broken space-inversion symmetry. These k -space magnetoelectric multipoles are reciprocal to the real-space charge dipoles associated with the broken inversion symmetry. Using the prototypical ferroelectric PbTiO 3 as an example, we show that their origin is a spin asymmetry in momentum space resulting from the broken space inversion symmetry associated with the ferroelectric polarization. In PbTiO 3 , the k -space spin asymmetry corresponds to a pure k -space magnetoelectric toroidal moment, which can be detected using magnetic Compton scattering, an established tool for probing magnetism in ferromagnets or ferrimagnets with a net spin polarization, which has not been exploited to date for nonmagnetic systems. In particular, the k -space magnetoelectric toroidal moment combined with the spin-orbit interaction manifest in an antisymmetric magnetic Compton profile that can be reversed using an electric field. Our work suggests an experimental route to directly measuring and tuning hidden k -space magnetoelectric multipoles via specially designed magnetic Compton scattering measurements.	Mar 2022
I05-ARPES	Signatures of weyl fermion annihilation in a correlated kagome magnet Ilya Belopolski , Tyler A. Cochran , Xiaoxiong Liu , Zi-Jia Cheng , Xian P. Yang , Zurab Guguchia , Stepan S. Tsirkin , Jia-Xin Yin , Praveen Vir , Gohil S. Thakur , Songtian S. Zhang , Junyi Zhang , Konstantine Kaznatcheev , Guangming Cheng , Guoqing Chang , Daniel Multer , Nana Shumiya , Maksim Litskevich , Elio Vescovo , Timur K. Kim , Cephise Cacho , Nan Yao , Claudia Felser , Titus Neupert , M. Zahid Hasan Physical Review Letters 127 DOI: 10.1103/PhysRevLett.127.256403 Diamond Proposal Number(s): [17924, 19313] Show Abstract ▼ Abstract: The manipulation of topological states in quantum matter is an essential pursuit of fundamental physics and next-generation quantum technology. Here we report the magnetic manipulation of Weyl fermions in the kagome spin-orbit semimetal Co 3 Sn 2 S 2 , observed by high-resolution photoemission spectroscopy. We demonstrate the exchange collapse of spin-orbit-gapped ferromagnetic Weyl loops into paramagnetic Dirac loops under suppression of the magnetic order. We further observe that topological Fermi arcs disappear in the paramagnetic phase, suggesting the annihilation of exchange-split Weyl points. Our findings indicate that magnetic exchange collapse naturally drives Weyl fermion annihilation, opening new opportunities for engineering topology under correlated order parameters.	Dec 2021
I13-2-Diamond Manchester Imaging	Dynamic multicontrast X-ray imaging method applied to additive manufacturing Lorenzo Massimi , Samuel J. Clark , Sebastian Marussi , Adam Doherty , Joachim Schulz , Shashidhara Marathe , Christoph Rau , Marco Endrizzi , Peter D. Lee , Alessandro Olivo Physical Review Letters 127 DOI: 10.1103/PhysRevLett.127.215503 Diamond Proposal Number(s): [23760] Show Abstract ▼ Abstract: We present a dynamic implementation of the beam-tracking x-ray imaging method providing absorption, phase, and ultrasmall angle scattering signals with microscopic resolution and high frame rate. We demonstrate the method’s ability to capture dynamic processes with 22-ms time resolution by investigating the melting of metals in laser additive manufacturing, which has so far been limited to single-modality synchrotron radiography. The simultaneous availability of three contrast channels enables earlier segmentation of droplets, tracking of powder dynamic, and estimation of unfused powder amounts, demonstrating that the method can provide additional information on melting processes.	Nov 2021
I10-Beamline for Advanced Dichroism	Superposition of emergent monopole and antimonopole in CoTb thin films Yao Guang , Kejing Ran , Junwei Zhang , Yizhou Liu , Senfu Zhang , Xuepeng Qiu , Yong Peng , Xixiang Zhang , Markus Weigand , Joachim Gräfe , Gisela Schütz , Gerrit Van Der Laan , Thorsten Hesjedal , Shilei Zhang , Guoqiang Yu , Xiufeng Han Physical Review Letters 127 DOI: 10.1103/PhysRevLett.127.217201 Diamond Proposal Number(s): [23785] Show Abstract ▼ Abstract: A three-dimensional singular point that consists of two oppositely aligned emergent monopoles is identified in continuous CoTb thin films, as confirmed by complementary techniques of resonant elastic x-ray scattering, Lorentz transmission electron microscopy, and scanning transmission x-ray microscopy. This new type of topological defect can be regarded as a superposition of an emergent magnetic monopole and an antimonopole, around which the source and drain of the magnetic flux overlap in space. We experimentally prove that the observed spin twist seen in Lorentz transmission electron microscopy reveals the cross section of the superimposed three-dimensional structure, providing a straightforward strategy for the observation of magnetic singularities. Such a quasiparticle provides an excellent platform for studying the rich physics of emergent electromagnetism.	Nov 2021
	Hidden charge order in an iron oxide square-lattice compound Jung-Hwa Kim , Darren C. Peets , Manfred Reehuis , Peter Adler , Andrey Maljuk , Tobias Ritschel , Morgan C. Allison , Jochen Geck , Jose R. L. Mardegan , Pablo J. Bereciartua Perez , Sonia Francoual , Andrew Walters , Thomas Keller , Paula M. Abdala , Philip Pattison , Pinder Dosanjh , Bernhard Keimer Physical Review Letters 127 DOI: 10.1103/PhysRevLett.127.097203 Open Access Show Abstract ▼ Abstract: Since the discovery of charge disproportionation in the FeO 2 square-lattice compound Sr 3 Fe 2 O 7 by Mössbauer spectroscopy more than fifty years ago, the spatial ordering pattern of the disproportionated charges has remained “hidden” to conventional diffraction probes, despite numerous x-ray and neutron scattering studies. We have used neutron Larmor diffraction and Fe K -edge resonant x-ray scattering to demonstrate checkerboard charge order in the FeO 2 planes that vanishes at a sharp second-order phase transition upon heating above 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens the corresponding superstructure reflections and greatly reduces their amplitude, thus explaining the difficulty of detecting them by conventional probes. We discuss the implications of these findings for research on “hidden order” in other materials.	Aug 2021
	Ultrawide temperature range super-invar behavior of R2(Fe,Co)17 materials (R = rare earth) Yili Cao , Kun Lin , Sergii Khmelevskyi , Maxim Avdeev , Keith M. Taddei , Qiang Zhang , Qingzhen Huang , Qiang Li , Kenichi Kato , Chiu Chung Tang , Alexandra Gibbs , Chin-Wei Wang , Jinxia Deng , Jun Chen , Hongjie Zhang , Xianran Xing Physical Review Letters 127 DOI: 10.1103/PhysRevLett.127.055501 Show Abstract ▼ Abstract: Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R 2 ( Fe , Co ) 17 materials ( R = rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3–461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3 d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve “ultrawide” SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials.	Jul 2021
I13-1-Coherence	X-ray ptychography with a laboratory source Darren Batey , Frederic Van Assche , Sander Vanheule , Matthieu N. Boone , Andrew J. Parnell , Oleksandr O. Mykhaylyk , Christoph Rau , Silvia Cipiccia Physical Review Letters 126 DOI: 10.1103/PhysRevLett.126.193902 Open Access Show Abstract ▼ Abstract: X-ray ptychography has revolutionized nanoscale phase contrast imaging at large-scale synchrotron sources in recent years. We present here the first successful demonstration of the technique in a small-scale laboratory setting. An experiment was conducted with a liquid metal-jet x-ray source and a single photon-counting detector with a high spectral resolution. The experiment used a spot size of 5 μ m to produce a ptychographic phase image of a Siemens star test pattern with a submicron spatial resolution. The result and methodology presented show how high-resolution phase contrast imaging can now be performed at small-scale laboratory sources worldwide.	May 2021
I05-ARPES	Distinct Kondo screening behaviors in heavy fermion filled skutterudites with 4f1 and 4f2 configurations X. Lou , T. l. Yu , Y. h. Song , C. h. P. Wen , W. z. Wei , A. Leithe-Jasper , Z. f. Ding , L. Shu , S. Kirchner , H. C. Xu , R. Peng , D. L. Feng Physical Review Letters 126 DOI: 10.1103/PhysRevLett.126.136402 Diamond Proposal Number(s): [22518] Show Abstract ▼ Abstract: CeOs 4 Sb 12 (COS) and PrOs 4 Sb 12 (POS) are two representative compounds that provide the ideal vantage point to systematically study the physics of multi- f -electron systems. COS with Ce 4 f 1 , and POS with Pr 4 f 2 configurations show distinct properties of Kondo insulating and heavy fermion superconductivity, respectively. We unveiled the underlying microscopic origin by angle-resolved photoemission spectroscopy studies. Their eV-scale band structure matches well, representing the common characters of conduction electrons in R Os 4 Sb 12 systems ( R = rare earth ). However, f electrons interact differently with conduction electrons in COS and POS. Strong hybridization between conduction electrons and f electrons is observed in COS with band dependent hybridization gaps, and the development of a Kondo insulating state is directly revealed. Although the ground state of POS is a singlet, finite but incoherent hybridization exists, which can be explained by the Kondo scattering with the thermally excited triplet crystalline electric field state. Our results help us to understand the intriguing properties in COS and POS, and provide a clean demonstration of the microscopic differences in heavy fermion systems with 4 f 1 and 4 f 2 configurations.	Apr 2021
I05-ARPES	Orbital complexity in intrinsic magnetic topological insulators MnBi4Te7 and MnBi6Te10 R. C. Vidal , H. Bentmann , J. i. Facio , T. Heider , P. Kagerer , C. I. Fornari , T. R. F. Peixoto , T. Figgemeier , S. Jung , Cephise Cacho , B. Büchner , J. Van Den Brink , C. M. Schneider , L. Plucinski , E. F. Schwier , K. Shimada , M. Richter , A. Isaeva , F. Reinert Physical Review Letters 126 DOI: 10.1103/PhysRevLett.126.176403 Diamond Proposal Number(s): [22468] Show Abstract ▼ Abstract: Using angle-resolved photoelectron spectroscopy (ARPES), we investigate the surface electronic structure of the magnetic van der Waals compounds MnBi 4 Te 7 and MnBi 6 Te 10 , the n = 1 and 2 members of a modular ( Bi 2 Te 3 ) n ( MnBi 2 Te 4 ) series, which have attracted recent interest as intrinsic magnetic topological insulators. Combining circular dichroic, spin-resolved and photon-energy-dependent ARPES measurements with calculations based on density functional theory, we unveil complex momentum-dependent orbital and spin textures in the surface electronic structure and disentangle topological from trivial surface bands. We find that the Dirac-cone dispersion of the topologial surface state is strongly perturbed by hybridization with valence-band states for Bi 2 Te 3 -terminated surfaces but remains preserved for MnBi 2 Te 4 -terminated surfaces. Our results firmly establish the topologically nontrivial nature of these magnetic van der Waals materials and indicate that the possibility of realizing a quantized anomalous Hall conductivity depends on surface termination.	Apr 2021

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