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Kramers Nodal Lines and Weyl Fermions in SmAlSi

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arXiv 2022年

作者： Zhang, Yichen Gao, Yuxiang Gao, Xue-Jian Lei, Shiming Ni, Zhuoliang Oh, Ji Seop Huang, Jianwei Yue, Ziqin Zonno, Marta Gorovikov, Sergey Hashimoto, Makoto Lu, Donghui Denlinger, Jonathan D. Birgeneau, Robert J. Kono, Junichiro Wu, Liang Law, Kam Tuen Morosan, Emilia Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong Department of Physics and Astronomy University of Pennsylvania PhiladelphiaPA19104 United States Department of Physics University of California BerkeleyCA94720 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Canadian Light Source Inc. 44 Innovation Boulevard SaskatoonSKS7N 2V3 Canada Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo ParkCA94025 United States Advanced Light Source Lawrence Berekeley National Laboratory BerkeleyCA94720 United States Materials Science Division Lawrence Berekeley National Laboratory BerkeleyCA94720 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Materials Science and Nanoengineering Rice University HoustonTX77005 United States

Kramers nodal lines (KNLs) have recently been proposed theoretically as a special type of Weyl line degeneracy connecting time-reversal invariant momenta. KNLs are robust to spin orbit coupling and are inherent to all non-centrosymmetric achiral crystal structures, leading to unusual spin, magneto-electric, and optical properties. However, their existence in in real quantum materials has not been experimentally established. Here we gather the experimental evidence pointing at the presence of KNLs in SmAlSi, a non-centrosymmetric metal that develops incommensurate spin density wave order at low temperature. Using angle-resolved photoemission spectroscopy, density functional theory calculations, and magneto-transport methods, we provide evidence suggesting the presence of KNLs, together with observing Weyl fermions under the broken inversion symmetry in the paramagnetic phase of SmAlSi. We discuss the nesting possibilities regarding the emergent magnetic orders in SmAlSi. Our results provide a solid basis of experimental observations for exploring correlated topology in SmAlSi. © 2022, CC BY-NC-SA.

关键词： Temperature

Spintronic superconductor in a bulk layered material with natural spin-valve structure

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arXiv 2020年

作者： Sakuragi, Shunsuke Sasaki, S. Akashi, R. Sakagami, R. Kuroda, K. Bareille, C. Hashimoto, T. Nagashima, T. Kinoshita, Y. Hirata, Y. Shimozawa, M. Asai, S. Yajima, T. Doi, S. Tsujimoto, N. Kunisada, S. Noguchi, R. Kurokawa, K. Azuma, N. Hirata, K. Yamasaki, Y. Nakao, H. Kim, T.K. Cacho, C. Masuda, T. Tokunaga, M. Wadati, H. Okazaki, K. Shin, S. Kamihara, Y. Yamashita, Minoru Kondo, Takeshi Institute for Solid State Physics University of Tokyo Kashiwa Chiba Japan Department of Physics University of Tokyo Tokyo Japan Department of Applied Physics and Phisico-Informatics Keio University Yokohama Japan Department of Applied Physics National Defense Academy of Japan Yokosuka Japan Division of Materials Physics Graduate School of Engineering Science Osaka University Toyonaka Japan Research Center for Computational Design of Advanced Functional Materials National Institute of Advanced Industrial Science and Technology Tsukuba Japan Research and Services Division of Materials Data and Integrated System National Institute for Materials Science Tsukuba Japan RIKEN Center for Emergent Matter Science Wako Japan PRESTO Japan Science and Technology Agency Kawaguchi Japan Condensed Matter Research Center and Photon Factory Institute of Materials Structure Science High Energy Accelerator Research Organization Tsukuba Japan Diamond Light Source Harwell Campus Didcot United Kingdom Graduate School of Material Science University of Hyogo Hyogo Japan TheUniversity of Tokyo Kashiwa Chiba277-8581 Japan Center for Spintronics Research Network Keio University Yokohama Japan

Multi-layered materials provide fascinating platforms to realize various functional properties, possibly leading to future electronic devices controlled by external fields. In particular, layered magnets coupled with conducting layers have been extensively studied recently for possible control of their transport properties via the spin structure. Successful control of quantum-transport properties in the materials with antiferromagnetic (AFM) layers, so-called natural spin-valve structure, has been reported for the Dirac Fermion and topological/axion materials [1-11]. However, a bulk crystal in which magnetic and superconducting layers are alternately stacked has not been realized until now, and the search for functional properties in it is an interesting yet unexplored field in material science. Here, we discover superconductivity providing such an ideal platform in EuSn2As2 with the van der Waals stacking of magnetic Eu layers and superconducting Sn-As layers, and present the first demonstration of a natural spin-valve effect on the superconducting current. Below the superconducting transition temperature (Tc), the electrical resistivity becomes zero in the in-plane direction. In contrast, it, surprisingly, remains finite down to the lowest temperature in the out-of-plane direction, mostly due to the structure of intrinsic magnetic Josephson junctions in EuSn2As2. The magnetic order of the Eu layers (or natural spin-valve) is observed to be extremely soft, allowing one to easy control of the out-of-plane to in-plane resistivities ratio from 1 to ∞ by weak external magnetic fields. The concept of multi-functional materials with stacked magnetic-superconducting layers will open a new pathway to develop novel spintronic devices with magnetically controllable superconductivity. Copyright © 2020, The Authors. All rights reserved.

关键词： Europium compounds

Electronic structure of the metallic antiferromagnet PdCrO2 measured by angle-resolved photoemission spectroscopy

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Physical Review B 2013年第12期88卷 125109-125109页

作者： J. A. Sobota K. Kim H. Takatsu M. Hashimoto S.-K. Mo Z. Hussain T. Oguchi T. Shishidou Y. Maeno B. I. Min Z.-X. Shen Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park California 94025 USA Geballe Laboratory for Advanced Materials Departments of Physics and Applied Physics Stanford University Stanford California 94305 USA Department of Physics Pohang University of Science and Technology Pohang 790-784 Korea Department of Physics Tokyo Metropolitan University Tokyo 192-0397 Japan Department of Physics Graduate School of Science Kyoto University Kyoto 606-8502 Japan Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park California 94025 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Institute of Scientific and Industrial Research Osaka University 8-1 Mihogaoka Ibaraki Osaka 567-0047 Japan Department of Quantum Matter ADSM Hiroshima University Higashi-Hiroshima 739-8530 Japan

PdCrO2 is material which has attracted interest due to the coexistence of metallic conductivity associated with itinerant Pd 4d electrons and antiferromagnetic order arising from localized Cr spins. A central issue is determining to what extent the magnetic order couples to the conduction electrons. Here we perform angle-resolved photoemission spectroscopy (ARPES) to experimentally characterize the electronic structure. We find that the Fermi surface has contributions from both bulk and surface states, which can be experimentally distinguished and theoretically verified by slab band structure calculations. The bulk Fermi surface shows no signature of electronic reconstruction in the antiferromagnetic state. This observation suggests that there is negligible interaction between the localized Cr spin structure and the itinerant Pd electrons measured by ARPES.

关键词： PHOTOEMISSION PHOTOELECTRICITY ELECTRIC conductivity ELECTRONS ANTIFERROMAGNETIC materials

Fabrication of Graphene By Electrochemical Exfoliation in Alkaline Electrolytes

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ECS Meeting Abstracts 2013年第41期MA2013-02卷

作者： Li-Chung Chang Yu-Chi Hsieh Yong-Min Chen Pu-Wei Wu Jyh-Fu Lee Graduate Program for Science and Technology of Accelerator Light Source National Chiao Tung University 1001 Ta Hsueh Road Hsinchu City Taiwan 300 Department of Materials Science and Engineering National Chiao Tung University 1001 Ta Hsueh Road Hsinchu City Taiwan 300 National Synchrotron Radiation Research Center 101 Hsin-Ann Road Hsinchu Science Park Hsin-Chu 30076 Taiwan ROC

Abstract not Available.

关键词：

Spectral evidence for unidirectional charge density wave in detwinned BaNi2As2

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Physical Review B 2023年第8期108卷 L081104-L081104页

作者： Yucheng Guo Mason Klemm Ji Seop Oh Yaofeng Xie Bing-Hua Lei Luca Moreschini Cheng Chen Ziqin Yue Sergey Gorovikov Tor Pedersen Matteo Michiardi Sergey Zhdanovich Andrea Damascelli Jonathan Denlinger Makoto Hashimoto Donghui Lu Chris Jozwiak Aaron Bostwick Eli Rotenberg Sung-Kwan Mo Rob G. Moore Junichiro Kono Robert J. Birgeneau David J. Singh Pengcheng Dai Ming Yi Department of Physics and Astronomy Rice University Houston Texas 77005 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics University of California Berkeley California 94720 USA Department of Physics and Astronomy University of Missouri Columbia Missouri 65211 USA Materials Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics University of Oxford Oxford OX1 3PU United Kingdom Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA Canadian Light Source Inc. 44 Innovation Boulevard Saskatoon SK S7N 2V3 Canada Department of Physics and Astronomy University of British Columbia Vancouver British Columbia V6T 1Z1 Canada Quantum Matter Institute University of British Columbia Vancouver British Columbia V6T 1Z4 Canada Max Planck Institute for Chemical Physics of Solids Nöthnitzer Straße 40 01187 Dresden Germany Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo Park California 94025 USA Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Smalley-Curl Institute Rice University Houston Texas 77005 USA Department of Materials Science and NanoEngineering Rice University Houston Texas 77005 USA Department of Chemistry University of Missouri Columbia Missouri 65211 USA

In the iron-based superconductors, unconventional superconductivity emerges in proximity to intertwined electronic orders consisting of an electronic nematic order and a spin density wave (SDW). Recently, BaNi2As2, like its well-known iron-based analog BaFe2As2, has been discovered to host a symmetry-breaking structural transition but coupled to a unidirectional charge density wave (CDW) instead of SDW, providing a novel platform to study intertwined orders. Here, through a systematic angle-resolved photoemission spectroscopy study combined with a detwinning B1g uniaxial strain, we identify distinct spectral evidence of band evolution due to the structural transition as well as CDW-induced band folding. In contrast to the nematicity and spin density wave in BaFe2As2, the structural and CDW order parameters in BaNi2As2 are observed to be strongly coupled and do not separate in the presence of uniaxial strain. Furthermore, no nematic band splitting is resolved above the structural transition. Our measurements point to a likely lattice origin of the CDW order in BaNi2As2.

关键词： Charge density waves Nematic phase transition Iron-based superconductors Angle-resolved photoemission spectroscopy

Weyl nodal ring states and Landau quantization with very large magnetoresistance in square-net magnet EuGa4

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arXiv 2022年

作者： Lei, Shiming Allen, Kevin Huang, Jianwei Moya, Jaime M. Wu, Tsz Chun Casas, Brian Zhang, Yichen Oh, Ji Seop Hashimoto, Makoto Lu, Donghui Denlinger, Jonathan Jozwiak, Chris Bostwick, Aaron Rotenberg, Eli Balicas, Luis Birgeneau, Robert Foster, Matthew S. Yi, Ming Sun, Yan Morosan, Emilia Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Rice University HoustonTX77005 United States National High Magnetic Field Laboratory TallahasseeFL32310 United States Department of Physics University of California BerkeleyCA94720 United States Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo ParkCA94025 United States Advanced Light Source Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Physics Florida State University TallahasseeFL32306 United States Materials Science Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Rice Center for Quantum Materials Rice University HoustonTX77005 United States Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences China

Magnetic topological semimetals (TSMs) allow for an effective control of the topological electronic states by tuning the spin configuration, and therefore are promising materials for next-generation electronic and spintronic applications. Of magnetic TSMs, Weyl nodal-line (NL) semimetals likely have the most tunability, and yet they are the least experimentally studied so far due to the scarcity of material candidates. Here, using a combination of angle-resolved photoemission spectroscopy and quantum oscillation measurements, together with density functional theory calculations, we identify the square-net compound EuGa4 as a new magnetic Weyl nodal ring (NR) semimetal, in which the line nodes form closed rings in the vicinity of the Fermi level. Remarkably, the Weyl NR states show distinct Landau quantization with clear spin splitting upon application of a magnetic field. At 2 K in a field of 14 T, the transverse magnetoresistance of EuGa4 exceeds 200,000%, which is more than two orders of magnitude larger than that of other known magnetic TSMs. High field magnetoresistance measurements indicate no saturation up to 40 T. Our theoretical model indicates that the nonsaturating MR naturally arises as a consequence of the Weyl NR state. Our work thus point to the realization of Weyl NR states in square-net magnetic materials, and opens new avenues for the design of magnetic TSMs with very large magnetoresistance. Copyright © 2022, The Authors. All rights reserved.

关键词： Density functional theory

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

The development of synchrotron-assisted scanning probe microscopy at NSRRC

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Journal of Physics: Conference Series 2013年第1期463卷

作者： Yuet-Loy Chan Xihui Liang Tsung-Hsuan Wu Dah-An Lu Meng-Fan Luo Yao-Jane Hsu D H Wei National Synchrotron Radiation Research Center Hsinchu 30076 Taiwan Department of Physics National Central University Taoyuan 32001 Taiwan Department of Physics National Sun Yat-sen University Kaohsiung 80424Taiwan Graduate Program for Science and Technology of Synchrotron Light Source National Tsing Hua University 30013 Hsinchu Taiwan

Synchrotron-based X-ray microspectroscopy is a technique that brings together microscopy and X-ray spectroscopy. It can be considered as an experimental approach capable of extracting X-ray spectrum from a finite area, or an alternative way of constructing images with spectroscopic contrast. The goal of this project is to integrate the functions of scanning tunnelling electron microscope (STM) with near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Here, we describe our experimental setup, followed by recent results that demonstrate the feasibility of acquiring NEXAFS spectrum with a SiO2 coated STM tip.

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Prominent Quasiparticle Peak in the Photoemission Spectrum of the Metallic Phase of V2O3

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Physical Review Letters 2003年第18期90卷 186403-186403页

作者： S.-K. Mo J. D. Denlinger H.-D. Kim J.-H. Park J. W. Allen A. Sekiyama A. Yamasaki K. Kadono S. Suga Y. Saitoh T. Muro P. Metcalf G. Keller K. Held V. Eyert V. I. Anisimov D. Vollhardt Randall Laboratory of Physics University of Michigan Ann Arbor Michigan 48109 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Pohang Accelerator Laboratory Pohang 790-784 Korea Department of Physics Pohang University of Science and Technology Pohang 790-784 Korea Department of Material Physics Graduate School of Engineering Science Osaka University 1-3 Machikaneyama Toyonaka Osaka 560-8531 Japan Department of Synchrotron Radiation Research Japan Atomic Energy Research Institute SPring-8 Sayo Hyogo 679-5143 Japan Japan Synchrotron Radiation Research Institute SPring-8 Sayo Hyogo 679-5143 Japan Department of Physics Purdue University West Lafayette Indiana 47907 USA Theoretical Physics III Center for Electronic Correlations and Magnetism University of Augsburg 86135 Augsburg Germany Max Planck Institute for Solid State Research Heisenbergstrasse 1 D-70569 Stuttgart Germany Theoretical Physics II University of Augsburg 86135 Augsburg Germany Institute of Metal Physics Ekaterinburg GSP-170 Russia

We present the first observation of a prominent quasiparticle peak in the photoemission spectrum of the metallic phase of V2O3 and report new spectral calculations that combine the local-density approximation with the dynamical mean-field theory (using quantum Monte Carlo simulations) to show the development of such a distinct peak with decreasing temperature. The experimental peak width and weight are significantly larger than in the theory.

关键词： Vanadium compounds