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Laser-based angle-resolved photoemission spectroscopy with micrometer spatial resolution and detection of three-dimensional spin vector

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arXiv 2023年

作者： Iwata, Takuma Kousa, T. Nishioka, Y. Ohwada, K. Sumida, K. Annese, E. Kakoki, M. Kuroda, Kenta Iwasawa, H. Arita, M. Kumar, S. Kimura, A. Miyamoto, K. Okuda, T. Graduate School of Advanced Science and Engineering Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima739-8526 Japan Hiroshima University Higashihiroshima739-8526 Japan Materials Sciences Research Center Japan Atomic Energy Agency Hyogo Sayo-gun679-5148 Japan Brasilian Center for Physical Science R. Dr. Xavier Sigaud 150 - Urca RJ Rio de Janeiro22290-180 Brazil Institute for Advanced Synchrotron Light Source National Institutes for Quantum Science and Technology Sendai980-8579 Japan Synchrotron Radiation Research Center National Institutes for Quantum Science and Technology Hyogo679-5148 Japan Hiroshima Synchrotron Radiation Center Hiroshima University 2-313 Kagamiyama Higashi-Hiroshima739-0046 Japan

We have developed a state-of-the-art apparatus for laser-based spin- and angle-resolved photoemission spectroscopy with micrometer spatial resolution (µ-SARPES). This equipment is achieved through the combination of a high-resolution photoelectron spectrometer, a 6-eV laser with high photon flux that is focused down to a few micrometers, a high-precision sample stage control system, and a double very-low-energy-electron-diffraction spin detector. The setup achieves an energy resolution of 1.5 (5.5) meV without (with) the spin detection mode, compatible with a spatial resolution better than 10 µm. This enables us to probe both spatially-resolved electronic structures and vector information of spin polarization in three dimensions. The performance of µ-SARPES apparatus is demonstrated by presenting ARPES and SARPES results from topological insulators and Au photolithography patterns on a Si (001) substrate. Copyright © 2023, The Authors. All rights reserved.

关键词： Micrometers

Spontaneous spin chirality reversal and competing phases in the topological magnet EuAl4

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arXiv 2024年

作者： Vibhakar, A.M. Khalyavin, D.D. Orlandi, F. Moya, J.M. Lei, S. Morosan, E. Bombardi, A. Diamond Light Source Ltd Harwell Science and Innovation Campus Didcot OxfordshireOX11 0DE United Kingdom ISIS facility Rutherford Appleton Laboratory-STFC Chilton DidcotOX11 0QX United Kingdom Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Hong Kong University of Science and Technology Clear Water Bay Hong Kong

We demonstrate the spontaneous reversal of spin chirality in a single crystal sample of the inter-metallic magnet EuAl4. We solve the nanoscopic nature of each of the four magnetically phases of EuAl4 using resonant magnetic x-ray scattering, and demonstrate all four phases order with single-k incommensurate magnetic modulation vectors. Below 15.4 K the system forms a spin density modulated spin structure where the spins are orientated in the ab plane perpendicular to the orientation of the magnetic propagation vector. Below 13.2 K a second spin density wave orders with moments aligned parallel to the c-axis, such that the two spin density wave orders coexist. Below 12.2 K a magnetic helix of a single chirality is stabilised across the entire sample. Below 10 K the chirality of the magnetic helix reverses, and the sample remains a single chiral domain. Concomitant with the establishment of the helical magnetic ordering is the lowering of the crystal symmetry to monoclinic, as evidenced the formation of uniaxial charge and spin strip domains. A group theoretical analysis demonstrates that below 12.2 K the symmetry lowers to polar monoclinic, which is necessary to explain the observed asymmetry in the chiral states of the magnetic helix and the spin chiral reversal. We find that in every magnetically ordered phase of EuAl4 the in-plane moment is perpendicular to the orientation of the magnetic propagation vector, which we demonstrate is favoured by magnetic dipolar interactions. Copyright © 2024, The Authors. All rights reserved.

关键词： Aluminum alloys

Spectral phase interferometry for direct electric-field reconstruction of synchrotron radiation

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arXiv 2022年

作者： Fuji, Takao Kaneyasu, Tatsuo Fujimoto, Masaki Okano, Yasuaki Salehi, Elham Hosaka, Masahito Takashima, Yoshifumi Mano, Atsushi Hikosaka, Yasumasa Wada, Shin-Ichi Katoh, Masahiro Laser Science Laboratory Toyota Technological Institute Nagoya468–8511 Japan SAGA Light Source Tosu841-0005 Japan Institute for Molecular Science Okazaki444-8585 Japan Synchrotron Radiation Research Center Nagoya University Nagoya464-0814 Japan National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China Institute of Liberal Arts and Sciences University of Toyama Toyama930-0194 Japan Graduate School of Advanced Science and Engineering Hiroshima University Higashi-Hiroshima739-8526 Japan Hiroshima Synchrotron Radiation Center Hiroshima University Higashi-Hiroshima739-0046 Japan

Ultraviolet and extreme ultraviolet electric-fields produced by relativistic electrons in an undulator of a synchrotron light source are characterized by using spectral phase interferometry for direct electric-field reconstruction (SPIDER). A tandem undulator with a phase shifter produces a pair of wavelength shifted wave packets with some delay. The interferogram between the pair of the wave packets is analyzed with a SPIDER algorithm, which is widely used for ultrashort pulse characterization. As a result, a 10-cycle square shaped electric-field is reconstructed. The waveform corresponds to the radiation from an electron accelerated with the undulator which consists of 10 periods of permanent magnets. © 2022, CC BY.

关键词： synchrotron radiation

Three-dimensional electronic structure in ferromagnetic Fe3Sn2 with breathing kagome bilayers

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Physical Review B 2020年第16期101卷 161114(R)-161114(R)页

作者： Hiroaki Tanaka Yuita Fujisawa Kenta Kuroda Ryo Noguchi Shunsuke Sakuragi Cédric Bareille Barnaby Smith Cephise Cacho Sung Won Jung Takayuki Muro Yoshinori Okada Takeshi Kondo ISSP University of Tokyo Kashiwa Chiba 277-8581 Japan Okinawa Institute of Science and Technology Graduate University Okinawa 904-0495 Japan Diamond Light Source Harwell Campus Didcot OX11 0DE United Kingdom Japan Synchrotron Radiation Research Institute (JASRI) 1-1-1 Kouto Sayo Hyogo 679-5198 Japan Trans-scale Quantum Science Institute University of Tokyo Bunkyo-ku Tokyo 113-0033 Japan

A large anomalous Hall effect (AHE) has been observed in ferromagnetic Fe3Sn2 with breathing kagome bilayers. To understand the underlying mechanism for this, we investigate the electronic structure of Fe3Sn2 by angle-resolved photoemission spectroscopy (ARPES). In particular, we use both vacuum ultraviolet light (VUV) and soft x ray (SX), which allow surface-sensitive and relatively bulk-sensitive measurements, respectively, and distinguish bulk states from surface states, which should be unlikely related to the AHE. While VUV-ARPES observes two-dimensional bands mostly due to surface states, SX-ARPES reveals three-dimensional band dispersions with a periodicity of the rhombohedral unit cell in the bulk. Our data show a good consistency with a theoretical calculation based on density functional theory, suggesting a possibility that Fe3Sn2 is a magnetic Weyl semimetal.

关键词： Anomalous Hall effect Bilayers Electronic structure Topological materials Ferromagnets Angle-resolved photoemission spectroscopy

Catalytically altering the redox pathway of sulfur in propylene carbonate electrolyte using dual-nitrogen/oxygen-containing carbon

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Chinese Journal of Catalysis 2024年第8期63卷 224-233页

作者： Linghui Yu Heng Zhang Luyuan Paul Wang Samuel Jun Hoong Ong Shibo Xi Bo Chen Rui Guo Ting Wang Yonghua Du Wei Chen Ovadia Lev Zhichuan J.Xu School of Chemistry and Chemical Engineering Wuhan Textile UniversityWuhan 430200HubeiChina School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore Hubei Key Laboratory of Biomass Fibers&Eco-Dyeing&Finishing Wuhan Textile UniversityWuhan 430200HubeiChina Institute of Sustainability for Chemicals Energy and Environment(ISCE2)Agency for ScienceTechnology and Research in Singapore(A*STAR)1 Pesek RoadJurong Island 627833Singapore Department of Chemistry National University of SingaporeSingapore 117543Singapore College of the Environment&Ecology Xiamen UniversityXiamen 361102FujianChina National Synchrotron Light Source II Brookhaven National LaboratoryUptonNY 11973USA The Institute of Chemistry The Hebrew University of JerusalemJerusalem 9190401Israel Singapore-HUJ Alliance for Research and Enterprise NEW-CREATE Phase IICampus for Research Excellence and Technological Enterprise(CREATE)Singapore138602Singapore Energy Research Institute@NTU ERI@NInterdisciplinary Graduate SchoolNanyang Technological UniversitySingapore 639798Singapore

Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion *** low-polysulfide-solubility feature of some carbonate solvents also makes them very promising for overcoming the shuttle effects of ***,regular sulfur electrodes experience undesired electrochemical mechanisms in carbonate electrolytes due to side *** this study,we report a catalytic redox mechanism of sulfur in propylene carbonate(PC)electrolyte based on a compari-son *** catalytic mechanism is characterized by the interactions between polysulfides and dual N/O functional groups on the host carbon,which largely prevents side reactions between polysulfides and the carbonate *** a mechanism coupled with the low-polysulfide-solubility feature leads to stable cycling of LSBs in PC *** dual N/O functional groups are identified via a density functional theory *** work provides an alternative route for enabling LSBs in carbonate electrolytes.

关键词： Energy storage Lithium-sulfur battery Catalytic redox reaction Porous carbon Carbonate electrolyte

Manipulation of the nanoscale heliconical structure of a twist-bend nematic material with polarized light

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Physical Review Research 2020年第3期2卷 032004(R)-032004(R)页

作者： C. Feng J. Feng R. Saha Y. Arakawa J. Gleeson S. Sprunt C. Zhu A. Jákli Chemical Physics Interdisciplinary Program Advanced Materials and Liquid Crystal Institute Kent State University Kent Ohio 44242 USA Advanced Light Source Lawrence Berkeley National Lab Berkeley California 94720 USA Department of Physics Kent State University Kent Ohio 44242 USA Department of Applied Chemistry and Life Science Graduate School of Engineering Toyohashi University of Technology Toyohashi 441-8580 Japan

The effect of polarized violet light on the alignment and the heliconical pitch of a liquid crystal dimer containing both sulfur atoms and an azo linkage has been studied by tender resonant x-ray scattering. The results provide evidence of the manipulation of the nanoscale heliconical structure by polarized light. In addition to the bulk alignment of the heliconical nanostructure, the value of the heliconical pitch can be varied as well. After turning the light on, an increase of the pitch is observed in two steps. The increase with a subsecond timescale is attributed to the reduced heliconical order related to trans-cis photoisomerization. This is followed by a smaller increase over a 10-s timescale, which is likely related to the annihilation of defects. After turning the light off, the pitch first decreases within a few seconds to a value larger than the original (before illumination), and then relaxes further on a much longer (hours) timescale.

关键词： Chiral symmetry Dynamical phase transitions Twist deformation

Surface valence transition in SmS by alkali metal adsorption

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arXiv 2022年

作者： Nakamura, Takuto Nakaya, Toru Ohtsubo, Yoshiyuki Sugihara, Hiroki Tanaka, Kiyohisa Yukawa, Ryu Kitamura, Miho Kumigashira, Hiroshi Imura, Keiichiro Suzuki, Hiroyuki S. Sato, Noriaki K. Kimura, Shin-Ichi Graduate School of Frontier Biosciences Osaka University Suita565-0871 Japan Department of Physics Graduate School of Science Osaka University Toyonaka560-0043 Japan Institute for Advances Synchrotron Light Source National Institutes for Quantum Science and Technology Sendai980-8579 Japan Institute for Molecular Science Okazaki444-8585 Japan Graduate School of Engineering Osaka University Suita565-0871 Japan 1-1 Oho Tsukuba305-0801 Japan Tohoku University Sendai980-8577 Japan Department of Physics Nagoya University Nagoya464-8602 Japan Institute for Solid State Physics The University of Tokyo Kashiwa277-8581 Japan Center for General Education Aichi Institute of Technology Toyota470-0392 Japan

The electronic structure changes of SmS surfaces under potassium (K) doping are elucidated using synchrotron-based core-level photoelectron spectroscopy and angle-resolved photoelectron spectroscopy (ARPES). The Sm core-level and ARPES spectra indicate that the Sm mean valence of the surface increased from the nearly divalent to trivalent states, with increasing K deposition. Carrier-induced valence transition (CIVT) from Sm2+ to Sm3+ exhibits a behavior opposite to that under conventional electron doping. Excess electrons are trapped by isolated excitons, which is inconsistent with the phase transition from the black insulator with Sm2+ to the gold metal with Sm3+ under pressure. This CIVT helps to clarify the pressure-induced black-to-golden phase transition in this material, which originates from the Mott transition of excitons. © 2022, CC BY.

关键词： Electronic structure

Fluctuated spin-orbital texture of Rashba-split surface states in real and reciprocal space

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arXiv 2021年

作者： Nakamura, Takuto Ohtsubo, Yoshiyuki Harasawa, Ayumi Yaji, Koichiro Shin, Shik Komori, Fumio Kimura, Shin-Ichi Graduate School of Frontier Biosciences Osaka University Suita565-0871 Japan Department of Physics Graduate School of Science Osaka University Toyonaka560-0043 Japan Institute for Advances Synchrotron Light Source National Institutes for Quantum Science and Technology Sendai980-8579 Japan Institute for Solid State Physics The University of Tokyo Kashiwa277-8581 Japan Ibaraki Tsukuba305-0003 Japan Institute for Molecular Science Okazaki444-8585 Japan

Spin-orbit interaction (SOI) in low-dimensional systems, namely Rashba systems and the edge states of topological materials, is extensively studied in this decade as a promising source to realize various fascinating spintronic phenomena, such as the source of the spin current and spin-mediated energy conversion. Here, we show the odd fluctuation in the spin-orbital texture in a surface Rashba system on Bi/InAs(110)-(2×1) by spin- and angle-resolved photoelectron spectroscopy and a numerical simulation based on a density-functional theory (DFT) calculation. The surface state shows a paired parabolic dispersion with the spin degeneracy lifted by the Rashba effect. Although its spin polarization should be fixed in a particular direction based on the Rashba model, the observed spin polarization varies greatly and even reverses its sign depending on the wavenumber. DFT calculations also reveal that the spin directions of two inequivalent Bi chains on the surface change from nearly parallel (canted-parallel) to anti-parallel in real space in the corresponding wavevector region. These results point out an oversimplification of the nature of spin in Rashba and Dirac systems and provide more freedom than expected for spin manipulation of photoelectrons. © 2021, CC BY.

关键词： Spin polarization

Ubiquitous Flat Bands in a Cr-based Kagome Superconductor

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arXiv 2024年

作者： Guo, Yucheng Wang, Zehao Xie, Fang Huang, Yuefei Gao, Bin Oh, Ji Seop Wu, Han Liu, Zhaoyu Ren, Zheng Fang, Yuan Biswas, Ananya Zhang, Yichen Yue, Ziqin Hu, Cheng Jozwiak, Chris Bostwick, Aaron Rotenberg, Eli Hashimoto, Makoto Lu, Donghui Kono, Junichiro Chu, Jiun-Haw Yakobson, Boris I. Birgeneau, Robert J. Si, Qimiao Dai, Pengcheng Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Advanced Light Source Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Department of Physics University of California BerkeleyCA94720 United States Department of Physics University of Washington Washington98105 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo ParkCA94025 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

In the quest for novel quantum states driven by topology and correlation, kagome lattice materials have garnered significant interest due to their distinctive electronic band structures, featuring flat bands (FBs) arising from the quantum destructive interference of the electronic wave function. The tuning of the FBs to the chemical potential would lead to the possibility of liberating electronic instabilities that lead to emergent electronic orders. Despite extensive studies, direct evidence of FBs tuned to the chemical potential and their participation in emergent electronic orders have been lacking in bulk quantum materials. Here using a combination of Angle-Resolved Photoemission Spectroscopy (ARPES) and Density Functional Theory (DFT), we reveal that the low-energy electronic structure of the recently discovered Cr-based kagome metal superconductor CsCr3Sb5 is dominated by a pervasive FB in close proximity to, and below the Fermi level. A comparative analysis with orbital-projected DFT and polarization dependence measurement uncovers that an orbital-selective renormalization mechanism is needed to reconcile the discrepancy with the DFT calculations, which predict the FB to appear 200 meV above the Fermi level. Furthermore, we observe the FB to shift away from the Fermi level by 20 meV in the low-temperature density wave-ordered phase, highlighting the role of the FB in the emergent electronic order. Our results reveal CsCr3Sb5 to stand out as a promising platform for further exploration into the effects of FBs near the Fermi level on kagome lattices, and their role in emergent orders in bulk quantum materials. © 2024, CC BY.

关键词： Density functional theory