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arXiv 2021年

作者： Oudich, Mourad Su, Guangxu Deng, Yuanchen Benalcazar, Wladimir Huang, Renwen Gerard, Nikhil J.R.K. Lu, Minghui Zhan, Peng Jing, Yun Graduate Program in Acoustics The Pennsylvania State University University ParkPA16802 United States Université de Lorraine CNRS Institut Jean Lamour NancyF-54000 France National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China School of Physics Nanjing University Nanjing210093 China Department of Physics The Pennsylvania State University University ParkPA16801 United States Department of Mechanical and Aerospace Engineering North Carolina State University RaleighNC27695 United States Department of Materials Science and Engineering Nanjing University NanjingJiangsu210093 China

Drawing inspiration from bilayer graphene, this paper introduces its photonic analog comprising two stacked graphene-like photonic crystals, that are coupled in the near-field through spoof surface plasmons. Beyond the twist degree of freedom that can radically alter the band structure of the bilayer photonic graphene, the photonic dispersion can be also tailored via the interlayer coupling which exhibits an exponential dependence on the distance between the two photonic crystals. We theoretically, numerically, and experimentally characterize the band structures of AA- and AB-stacked bilayer photonic graphene, as well as for twisted bilayer photonic graphene with even and odd sublattice exchange symmetries. Furthermore, we numerically predict the existence of magic angles in bilayer photonic graphene, which are associated with ultra-flat bands resulted from interlayer hybridization. Finally, we demonstrate that the bilayer photonic graphene at a particular twist angle satisfying even sublattice exchange symmetry is a high-order photonic topological insulator. The proposed bilayer photonic graphene could constitute a useful platform for identifying new quantum materials and inspiring next-generation photonic devices with new degrees of freedom and emerging functionality. © 2021, CC BY.

关键词： Graphene

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Generation of Terahertz Transients from Co2Fe0.4Mn0.6Si Heusler alloy/Heavy-Metal Bilayers

Generation of Terahertz Transients from Co2Fe0.4Mn0.6Si Heus...

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International Conference on Infrared and Millimeter Waves

作者： S. Heidtfeld R. Adam T. Kubota K. Takanashi S. Suga D. Cao C. Greb F. Wang C. Schmitz-Antoniak D.E. Bürgler G. Chen I. Komissarov R. Sobolewski C. M. Schneider Research Centre Jülich Peter Grünberg Institute Jülich Germany University Duisburg-Essen Duisburg Germany Institute for Materials Research Tohoku University Sendai Japan Center for Spintronics Research Network Tohoku University Sendai Japan Center for Science and Innovation in Spintronics (Core Research Cluster) Tohoku University Sendai Japan Institute of Scientific and Industrial Research Osaka University Ibaraki Japan College of Physics National Demonstration Center for Applied Physics Education Qindao University Qingdao China Materials Science Graduate Program University of Rochester Rochester New York USA University of Rochester Rochester New York USA Belarusian State University of Informatics and Radioelectronics Minsk Belarus University of California Davis Davis California USA

We generated electro magnetic transients with a frequency content up to the terahertz regime from Co 2 Fe 0.4 Mn 0.6 Si Heusler alloy/heavy-metal bilayers by excitation with fs-laser pulses. We ascribe the generation process to the inverse spin Hall effect. We compared our results with ferromagnetic resonance measurements to investigate the efficiency of interfacial spin currents. We observed that the efficiency of the THz radiation can be described by the spin-orbit coupling, nonetheless the interface properties play an important role.

关键词： Ferromagnetic resonance Couplings Current measurement Hall effect Transient analysis

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Generation of terahertz transients from Co2Fe0.4Mn0.6Si-Heusler-alloy/normal-metal nanobilayers excited by femtosecond optical pulses

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Physical Review Research 2021年第4期3卷 043025-043025页

作者： Sarah Heidtfeld Roman Adam Takahide Kubota Koki Takanashi Derang Cao Carolin Schmitz-Antoniak Daniel E. Bürgler Fangzhou Wang Christian Greb Genyu Chen Ivan Komissarov Hilde Hardtdegen Martin Mikulics Roman Sobolewski Shigemasa Suga Claus M. Schneider Research Centre Jülich Peter Grünberg Institute 52425 Jülich Germany Faculty of Physics University of Duisburg-Essen 47048 Duisburg Germany Institute for Materials Research Tohoku University Sendai 980-8577 Japan Center for Spintronics Research Network Tohoku University Sendai 980-8577 Japan Center for Science and Innovation in Spintronics (Core Research Cluster) Tohoku University Sendai 980-8577 Japan College of Physics National Demonstration Center for Experimental Applied Physics Education Qingdao University Qingdao 266071 China Materials Science Graduate Program University of Rochester Rochester New York 14627 USA Laboratory for Laser Energetics University of Rochester Rochester New York 14623 USA Department of Electrical and Computer Engineering University of Rochester Rochester New York 14627 USA Belarusian State University of Informatics and Radioelectronics Minsk 220013 Belarus Research Centre Jülich Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons 52425 Jülich Germany Department of Physics and Astronomy University of Rochester Rochester New York 14627 USA The Institute of Scientific and Industrial Research Osaka University Ibaraki Osaka 567-0047 Japan Department of Physics University of California Davis Davis California 95616 USA

We generated pulses of electromagnetic radiation in the terahertz (THz) frequency range by optical excitation of Co2Fe0.4Mn0.6Si (CFMS)/normal-metal (NM) bilayer structures. The CFMS is a Heusler alloy showing a band gap in one spin channel and is therefore a half metal. We compared the THz emission efficiency in a systematic manner for four different CFMS/NM bilayers, where NM was either Pt, Ta, Cr, or Al. Our measurements show that the THz intensity is highest for a Pt capping. We also demonstrate the tunability of the THz amplitude by varying the magnetic field for all four bilayers. We attribute the THz generation to the inverse spin Hall effect. In order to investigate the role of the interface in THz generation, we measured the spin mixing conductance for each CFMS/NM bilayer using a ferromagnetic resonance method. We found that the spin-orbit coupling cannot completely describe the THz generation in the bilayers and that the spin transmission efficiency of the CFMS/NM interface and the spin diffusion length, as well as the oxidation of the NM layer, play crucial roles in the THz emission process.

关键词： Inverse spin Hall effect Magnetism Spin injection Spin pumping Spintronics Ferromagnetic resonance Terahertz time-domain spectroscopy

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Inverse-designed silicon photonic circuit for nonreciprocal transmission

Inverse-designed silicon photonic circuit for nonreciprocal ...

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Frontiers in Optics, FIO 2019 - Part of Frontiers in Optics + Laser science APS/DLS

作者： Yang, Ki Youl Skarda, Jinhie Cotrufo, Michele Ahn, Geun Ho Alù, Andrea Vučković, Jelena E. L. Ginzton Laboratory Stanford University StanfordCA94305 United States Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712 United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States Department of Electrical Engineering City University of New York New YorkNY10031 United States

Broadband nonreciprocal transmission is demonstrated in an inverse-designed silicon photonic circuit. Cascaded nonlinear resonators break the single-resonator fundamental bound on forward transmission at wide nonrecip... 详细信息

ISBN: (纸本)9781943580675

关键词： Silicon photonics

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Virtual critical coupling

arXiv

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arXiv 2020年

作者： Ra'di, Younes Krasnok, Alex Alú, Andrea Photonics Initiative Advanced Science Research Center City University of New York NY10031 United States Physics Program Graduate Center City University of New York NY10016 United States Department of Electrical Engineering City College of The City University of New York NY10031 United States

Electromagnetic resonators are a versatile platform to harvest, filter and trap electromagnetic energy, at the basis of many applications from microwaves to optics. Resonators with a large intrinsic quality factor (Q) are highly desirable, since they can store a large amount of energy, leading to sharp filtering and low loss. Exciting high-Q cavities with monochromatic signals, however, suffers from poor excitation efficiency, i.e., most of the impinging energy is lost in the form of reflection, since high-Q resonators are weakly coupled to external radiation. Although critical coupling eliminates reflections in steady-state by matching the intrinsic and coupling decay rates, this approach requires the introduction of loss in the resonator, causing dissipation and lowering the overall Q-factor. Here, we extend the notion of critical coupling to high-Q lossless resonators based on tailoring the temporal profile of the excitation wave. Utilizing coupled-mode theory, we demonstrate an effect analogous to critical coupling by mimicking loss with non-monochromatic excitations at complex frequencies. Remarkably, we show that this approach enables unitary excitation efficiency in open systems, even in the limit of extreme quality factors in the regime of quasi-bound states in the continuum. Copyright © 2020, The Authors. All rights reserved.

关键词： Q factor measurement

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Magnetic Fields in Massive Star-forming Regions (MagMaR): Unveiling an Hourglass Magnetic Field in G333.46−0.16 using ALMA

arXiv

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arXiv 2024年

作者： Saha, Piyali Sanhueza, Patricio Padovani, Marco Girart, Josep M. Cortes, Paulo Morii, Kaho Liu, Junhao Sánchez-Monge, Á. Galli, Daniele Basu, Shantanu Koch, Patrick M. Beltrán, Maria T. Li, Shanghuo Beuther, Henrik Stephens, Ian W. Nakamura, Fumitaka Zhang, Qizhou Jiao, Wenyu Fernández-López, M. Hwang, Jihye Chung, Eun Jung Pattle, Kate Zapata, Luis A. Xu, Fengwei Olguin, Fernando A. Kang, Ji-Hyun Karoly, Janik Law, Chi-Yan Wang, Jia-Wei Csengeri, Timea Lu, Xing Cheng, Yu Kim, Jongsoo Choudhury, Spandan Chen, Huei-Ru Vivien Hull, Charles L.H. National Astronomical Observatory of Japan National Institutes of Natural Sciences 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Astronomical Science Program The Graduate University for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan INAF-Osservatorio Astrofisico di Arcetri Largo E. Fermi 5 Firenze50125 Italy Campus UAB Can Magrans S/N Cerdanyola del Vallés CataloniaE-08193 Spain PMT-UPC Esteve Terradas 1 Castelldefels CataloniaE-08860 Spain Joint ALMA Observatory Alonso de Córdova 3107 Vitacura Santiago Chile National Radio Astronomy Observatory 520 Edgemont Road CharlottesvilleVA22903 United States Department of Astronomy Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0033 Japan Department of Physics and Astronomy University of Western Ontario LondonONN6A 3K7 Canada Academia Sinica Institute of Astronomy and Astrophysics Taipei Taiwan INAF-Osservatorio Astrofisico di Arcetri Largo E. Fermi 5 FirenzeI-50125 Italy Max Planck Institute for Astronomy Königstuhl 17 HeidelbergD-69117 Germany Department of Earth Environment and Physics Worcester State University WorcesterMA01602 United States Department of Astronomy The University of Tokyo Hongo Tokyo113-0033 Japan 2-21-1 Osawa Mitaka Tokyo181-0015 Japan Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Haidian District Beijing100871 China C.C. No. 5 Villa Elisa Buenos Aires1894 Argentina Korea Astronomy and Space Science Institute 776 Daedeokdae-ro Yuseong-gu Daejeon34055 Korea Republic of Department of Physics and Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom Instituto de Radioastronomía y Astrofísica Universidad Nacional Autónoma de México P.O. Box 3-72 Michoacán Morelia58090 Mexico

The contribution of the magnetic field to the formation of high-mass stars is poorly understood. We report the high-angular resolution (∼ 0.3′′, 870 au) map of the magnetic field projected on the plane of the sky (Bpos) towards the high-mass star forming region G333.46−0.16 (G333), obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.2 mm as part of the Magnetic Fields in Massive Star-forming Regions (MagMaR) survey. The Bpos morphology found in this region is consistent with a canonical "hourglass" which suggest a dynamically important field. This region is fragmented into two protostars separated by ∼ 1740 au. Interestingly, by analysing H13CO+ (J = 3−2) line emission, we find no velocity gradient over the extend of the continuum which is consistent with a strong field. We model the Bpos, obtaining a marginally supercritical mass-to-flux ratio of 1.43, suggesting a initially strongly magnetized environment. Based on the Davis–Chandrasekhar–Fermi method, the magnetic field strength towards G333 is estimated to be 5.7 mG. The absence of strong rotation and outflows towards the central region of G333 suggests strong magnetic braking, consistent with a highly magnetized environment. Our study shows that despite being a strong regulator, the magnetic energy fails to prevent the process of fragmentation, as revealed by the formation of the two protostars in the central region. Copyright © 2024, The Authors. All rights reserved.

关键词： Magnetic fields

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Tunable plasmonic ultrastrong coupling: Emulating dicke physics at room temperature

arXiv

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arXiv 2021年

作者： Yahiaoui, Riad Chase, Zizwe A. Kyaw, Chan Tay, Fuyang Baydin, Andrey Noe, G. Timothy Song, Junyeob Kono, Junichiro Agrawal, Amit Bamba, Motoaki Searles, Thomas A. Department of Physics and Astronomy Howard University WashingtonDC20059 United States Department of Electrical and Computer Engineering Rice University HoustonTX70005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States Physical Measurement Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Maryland NanoCenter University of Maryland College ParkMD20742 United States The Hakubi Center for Advanced Research Kyoto University Kyoto606-8502 Japan Department of Physics I Kyoto University Kyoto606-8502 Japan Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States

A system of N two-level atoms cooperatively interacting with a photonic field can be described as a single giant atom coupled to the field with interaction strength ∝ √N. This enhancement, known as Dicke cooperativity in quantum optics, has recently become an indispensable element in quantum information technology based on strong light-matter coupling. Here, we extend the coupling beyond the standard light-matter interaction paradigm, emulating Dicke cooperativity in a terahertz metasurface with N meta-atoms. Cooperative enhancement manifested in the form of matter-matter coupling, through the hybridization of localized surface plasmon resonance in individual meta-atoms and surface lattice resonance due to the periodic array of the meta-atoms. By varying the lattice constant of the array, we observe a clear anticrossing behavior, a signature of strong coupling. Furthermore, through engineering of the capacitive split-gap in the meta-atoms, the coupling rate was cooperatively enhanced into the ultrastrong coupling regime by a factor of √N. This room-temperature technology serves as a convenient quantum emulator of the dynamics of a qubit with a giant dipole moment coherently driven by a single bosonic field. Copyright © 2021, The Authors. All rights reserved.

关键词： Atoms

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The ALCHEMI atlas: principal component analysis reveals starburst evolution in NGC 253

arXiv

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arXiv 2024年

作者： Harada, Nanase Meier, David S. Martín, Sergio Muller, Sebastien Sakamoto, Kazushi Saito, Toshiki Gorski, Mark D. Henkel, Christian Tanaka, Kunihiko Mangum, Jeffrey G. Aalto, Susanne Aladro, Rebeca Bouvier, Mathilde Colzi, Laura Emig, Kimberly L. Herrero-Illana, Rubén Huang, Ko-Yun Kohno, Kotaro König, Sabine Nakanishi, Kouichiro Nishimura, Yuri Takano, Shuro Rivilla, Víctor M. Viti, Serena Watanabe, Yoshimasa van der Werf, Paul P. Yoshimura, Yuki National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Institute of Astronomy and Astrophysics Academia Sinica 11F of AS/NTU Astronomy-Mathematics Building No.1 Sec. 4 Roosevelt Rd Taipei10617 Taiwan Astronomical Science Program Graduate Institute for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-1855 Japan New Mexico Institute of Mining and Technology 801 Leroy Place SocorroNM87801 United States National Radio Astronomy Observatory PO Box O 1003 Lopezville Road SocorroNM87801 United States European Southern Observatory Alonso de Córdova 3107 Vitacura Santiago763-0355 Chile Joint ALMA Observatory Alonso de Córdova 3107 Vitacura Santiago763-0355 Chile Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-439 92 Sweden Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 Bonn53121 Germany Astronomy Department Faculty of Science King Abdulaziz University P. O. Box 80203 Jeddah21589 Saudi Arabia Department of Physics Faculty of Science and Technology Keio University 3-14-1 Hiyoshi Kanagawa Yokohama223-8522 Japan National Radio Astronomy Observatory 520 Edgemont Road CharlottesvilleVA22903-2475 United States Department of Space Earth and Environment Chalmers University of Technology GöteborgSE-412 96 Sweden Leiden Observatory Leiden University P.O. Box 9513 Leiden2300 RA Netherlands CSIC-INTA Ctra. de Ajalvir Km. 4 Torrejón de Ardoz Madrid28850 Spain Campus UAB Carrer de Magrans BarcelonaE-08193 Spain Institute of Astronomy Graduate School of Science The University of Tokyo 2-21-1 Osawa Mitaka Tokyo181-0015 Japan Department of Astronomy The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-0033 Japan ALMA Project National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Department of Physic

Molecular lines are powerful diagnostics of the physical and chemical properties of the interstellar medium (ISM). These ISM properties, which affect future star formation, are expected to differ in starburst galaxies from those of more quiescent galaxies. We investigate the ISM properties in the central molecular zone of the nearby starburst galaxy NGC 253 using the ultra-wide millimeter spectral scan survey from the ALMA Large program ALCHEMI. We present an atlas of velocity-integrated images at a 1′′. 6 resolution of 148 unblended transitions from 44 species, including the first extragalactic detection of HCNH+ and the first interferometric images of C3H+, NO, HCS+. We conduct a principal component analysis (PCA) on these images to extract correlated chemical species and to identify key groups of diagnostic transitions. To the best of our knowledge, our dataset is currently the largest astronomical set of molecular lines to which PCA has been applied. The PCA can categorize transitions coming from different physical components in NGC 253 such as i) young starburst tracers characterized by high-excitation transitions of HC3N and complex organic molecules (COMs) versus tracers of on-going star formation (radio recombination lines) and high-excitation transitions of CCH and CN tracing PDRs, ii) tracers of cloud-collision-induced shocks (low-excitation transitions of CH3OH, HNCO, HOCO+, and OCS) versus shocks from star-formation-induced outflows (high-excitation transitions of SiO), as well as iii) outflows showing emission from HOC+, CCH, H3O+, CO isotopologues, HCN, HCO+, CS, and CN. Our findings show these intensities vary with galactic dynamics, star formation activities, and stellar feedback. © 2024, CC BY.

关键词： Principal component analysis

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Monitoring the pointing of the prototype LST-1 using star reconstruction in the Cherenkov camera

arXiv

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arXiv 2021年

作者： Abe, H. Aguasca, A. Agudo, I. Antonelli, L.A. Aramo, C. Armstrong, T. Artero, M. Asano, K. Ashkar, H. Aubert, P. Baktash, A. Bamba, A. Larriva, A. Baquero Baroncelli, L. de Almeida, U. Barres Barrio, J.A. Batkovic, I. González, J. Becerra Bernardos, M.I. Berti, A. Biederbeck, N. Bigongiari, C. Blanch, O. Bonnoli, G. Bordas, P. Bose, D. Bulgarelli, A. Burelli, I. Buscemi, M. Cardillo, M. Caroff, S. Carosi, A. Cassol, F. Cerruti, M. Chai, Y. Cheng, K. Chikawa, M. Chytka, L. Contreras, J.L. Cortina, J. Costantini, H. Dalchenko, M. de Angelis, A. de Bony de Lavergne, M. Deleglise, G. Delgado, C. Mengual, J. Delgado Volpe, D. della Depaoli, D. Di Pierro, F. Di Venere, L. Díaz, C. Dominik, R.M. Prester, D. Dominis Donini, A. Dorner, D. Doro, M. Elsässer, D. Emery, G. Escudero, J. Fiasson, A. Foffano, L. Fonseca, M.V. Coromina, L. Freixas Fukami, S. Fukazawa, Y. Garcia, E. López, R. Garcia Giglietto, N. Giordano, F. Gliwny, P. Godinovic, N. Green, D. Grespan, P. Gunji, S. Hackfeld, J. Hadasch, D. Hahn, A. Hassan, T. Hayashi, K. Heckmann, L. Heller, M. Llorente, J. Herrera Hirotani, K. Hoffmann, D. Horns, D. Houles, J. Hrabovsky, M. Hrupec, D. Hui, D. Hütten, M. Inada, T. Inome, Y. Iori, M. Ishio, K. Iwamura, Y. Jacquemont, M. Martinez, I. Jimenez Jouvin, L. Jurysek, J. Kagaya, M. Karas, V. Katagiri, H. Kataoka, J. Kerszberg, D. Kobayashi, Y. Kong, A. Kubo, H. Kushida, J. Lamanna, G. Lamastra, A. Le Flour, T. Longo, F. López-Coto, R. López-Moya, M. López-Oramas, A. Luque-Escamilla, P.L. Majumdar, P. Makariev, M. Mandat, D. Manganaro, M. Mannheim, K. Mariotti, M. Marquez, P. Marsella, G. Martí, J. Martinez, O. Martínez, G. Martínez, M. Marusevec, P. Mas, A. Maurin, G. Mazin, D. Guillen, E. Mestre Micanovic, S. Miceli, D. Miener, T. Miranda, J.M. Miranda, L.D.M. Mirzoyan, R. Mizuno, T. Molina, E. Montaruli, T. Monteiro, I. Moralejo, A. Morcuende, D. Moretti, E. Morselli, A. Mrakovcic, K. Murase, K. Nagai, A. Nakamori, T. Nickel, L. University of Geneva quai Ernest Ansermet 24 Geneva Switzerland Institute for Cosmic Ray Research University of Tokyo Departament de Física Quàntica i Astrofísica Institut de Ciències del Cosmos Universitat de Barcelona IEEC-UB Instituto de Astrofísica de Andalucía-CSIC INAF Osservatorio Astronomico di Roma INFN Sezione di Napoli Aix Marseille Univ CNRS IN2P3 CPPM The Barcelona Institute of Science and Technology IRFU CEA Université Paris-Saclay LAPP Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS-IN2P3 Annecy France Universität Hamburg Institut für Experimentalphysik Graduate School of Science University of Tokyo EMFTEL department IPARCOS Universidad Complutense de Madrid INAF Osservatorio di Astrofisica e Scienza dello Spazio di Bologna Centro Brasileiro de Pesquisas Físicas INFN Sezione di Padova Università degli Studi di Padova Instituto de Astrofísica de Canarias Departamento de Astrofísica Universidad de La Laguna Max-Planck-Institut für Physik Department of Physics TU Dortmund University Saha Institute of Nuclear Physics INFN Sezione di Trieste Università degli Studi di Udine INFN Sezione di Catania University of Geneva Département de Physique Nucléaire et Corpusculaire Palacky University Olomouc Faculty of Science CIEMAT Port d'Informació Científica INFN Sezione di Torino Dipartimento di Fisica Universitá degli Studi di Torino INFN Sezione di Bari Università di Bari University of Rijeka Department of Physics Institute for Theoretical Physics and Astrophysics Universität Würzburg Physics Program Graduate School of Advanced Science and Engineering Hiroshima University INFN Sezione di Bari Politecnico di Bari Faculty of Physics and Applied Informatics University of Lodz University of Split FESB Department of Physics Yamagata University Institut für Theoretische Physik Lehrstuhl IV: Plasma-Astroteilchenphysik Ruhr-Universität Bochum Tohoku University Astronomical Institute Josip Juraj Strossmayer University of Osijek Department of Physics INFN Sezione di Roma La

The first Large-Sized Telescope (LST-1) proposed for the forthcoming Cherenkov Telescope Array (CTA) has started to operate in 2019 in La Palma. The large structure of LST-1 - with a 23 m mirror dish diameter - imposes a strict control of its deformations that could affect the pointing accuracy and its overall performance. According to CTA specifications that are conceived to resolve e.g. the fine structure of galactic sources, the LST post-calibration pointing accuracy should be better than 14 arcseconds. To fulfill this requirement, the telescope pointing precision is monitored with two dedicated CCD cameras located at the dish center. The analysis of their images allows us to disentangle different systematic deformations of the structure. In this work, we investigate a complementary approach that offers the possibility to monitor the pointing of the telescope during the acquisition of sky data. After properly cleaning the events from the Cherenkov showers, the reconstructed positions of the stars imaged in the camera field of view are compared to their nominal expected positions in catalogues. This provides a direct measurement of the telescope pointing, that can be used to cross-check the other methods and as a real-time monitoring of the optical properties of the telescope and of the pointing corrections applied by the bending models. Additionally, this method benefits from not relying on specific hardware or dedicated observations. In this contribution we will illustrate this analysis and show results based on simulations of LST-1. Copyright © 2021, The Authors. All rights reserved.

关键词： Deformation

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Nonreciprocal interactions induced by water in confinement

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Physical Review Research 2020年第4期2卷 043244-043244页

作者： Felipe Jiménez-Ángeles Katherine J. Harmon Trung Dac Nguyen Paul Fenter Monica Olvera de la Cruz Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Applied Physics Graduate Program Northwestern University Evanston Illinois 60208 USA Department of Chemical and Biological Engineering Northwestern University Evanston Illinois 60208 USA Chemical Sciences and Engineering Division Argonne National Laboratory Lemont Illinois 60439 USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Chemistry Northwestern University Evanston Illinois 60208 USA

Water mediates electrostatic interactions via the orientation of its dipoles around ions, molecules, and interfaces. This induced water polarization consequently influences multiple phenomena. In particular, water polarization affects ion adsorption and transport, biomolecular self-assembly, and surface chemical reactions. Therefore, it is of paramount importance to understand water-mediated interactions modulated by nanoconfinement at the nanoscale. Here we investigate the effective interaction between two oppositely charged ions in different positions in water confined between two graphene surfaces. We find that the attraction between physisorbed ions is enhanced in the surface normal direction while the in-plane interaction is almost unaffected. The attraction in the surface normal direction is further enhanced by decreasing the confinement distance. Conversely, when one ion is intercalated into the graphene layers, the interaction becomes repulsive. Moreover, upon exchange of the ions' positions along the surface normal direction, the interaction energy changes by about 5kBT. The nonequivalent and directional properties found here, referred to as nonreciprocal interactions, cannot be explain by current water permittivity models in confinement. Our x-ray reflectivity experiments of the water structure near a graphene surface support our molecular dynamics simulation results. Our work shows that the water structure is not enough to infer electrostatic interactions near interfaces.

关键词： Confinement Dielectric properties Surface & interfacial phenomena Polarization Molecular dynamics X-ray reflectivity

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