检索结果-内蒙古大学图书馆

arXiv 2021年

作者： Abe, S. Asami, S. Gando, A. Gando, Y. Gima, T. Goto, A. Hachiya, T. Hata, K. Hosokawa, K. Ichimura, K. Ieki, S. Ikeda, H. Inoue, K. Ishidoshiro, K. Kamei, Y. Kawada, N. Kishimoto, Y. Kinoshita, T. Koga, M. Maemura, N. Mitsui, T. Miyake, H. Nakamura, K. Nakamura, K. Nakamura, R. Ozaki, H. Sakai, T. Sambonsugi, H. Shimizu, I. Shirai, J. Shiraishi, K. Suzuki, A. Suzuki, Y. Takeuchi, A. Tamae, K. Eizuka, M. Kurasawa, M. Nakahata, T. Futagi, S. Watanabe, H. Yoshida, Y. Obara, S. Ichikawa, A.K. Yoshida, S. Umehara, S. Fushimi, K. Berger, B.E. Fujikawa, B.K. Learned, J.G. Maricic, J. Axani, Spencer N. Smolsky, J. Laber-Smith, C. Winslow, L.A. Fu, Z. Ouellet, J. Efremenko, Y. Karwowski, H.J. Markoff, D.M. Tornow, W. Li, A. Detwiler, J.A. Enomoto, S. Decowski, M.P. Grant, C. Song, H. O'Donnell, T. Dell'Oro, S. Research Center for Neutrino Science Tohoku University Sendai980-8578 Japan Institute for the Physics and Mathematics of the Universe The University of Tokyo Kashiwa277-8568 Japan Graduate Program on Physics for the Universe Tohoku University Sendai980-8578 Japan Frontier Research Institute for Interdisciplinary Sciences Tohoku University Sendai980-8578 Japan Department of Physics Tohoku University Sendai980-8578 Japan Graduate School of Science Osaka University Osaka Toyonaka560-0043 Japan Osaka University Osaka Ibaraki567-0047 Japan Graduate School of Advanced Technology and Science Tokushima University Tokushima770-8506 Japan Nuclear Science Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Physics and Astronomy University of Hawaii at Manoa HonoluluHI96822 United States Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics and Astronomy University of Tennessee KnoxvilleTN37996 United States Triangle Universities Nuclear Laboratory DurhamNC27708 United States The University of North Carolina at Chapel Hill Chapel HillNC27599 United States North Carolina Central University DurhamNC27701 United States Department of Physics Duke University DurhamNC27705 United States Center for Experimental Nuclear Physics and Astrophysics University of Washington SeattleWA98195 United States Nikhef The University of Amsterdam Science Park Amsterdam Netherlands Boston University BostonMA02215 United States Center for Neutrino Physics Virginia Polytechnic Institute State University BlacksburgVA24061 United States

We present the results of a time-coincident event search for low-energy electron antineutrinos in the KamLAND detector with gamma-ray bursts from the Gamma-ray Coordinates Network and Fermi Gamma-ray Burst Monitor. Using a variable coincidence time window of ±500 s plus the duration of each gamma-ray burst, no statistically significant excess above background is observed. We place the world's most stringent 90% confidence level upper limit on the electron antineutrino fluence below 17.5 MeV. Assuming a Fermi-Dirac neutrino energy spectrum from the gamma-ray burst source, we use the available redshift data to constrain the electron antineutrino luminosity and effective temperature. Copyright © 2021, The Authors. All rights reserved.

关键词： Stars

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Nonlinear spectroscopy of random quantum magnets

arXiv

引用

arXiv 2020年

作者： Parameswaran, S.A. Gopalakrishnan, S. Rudolf Peierls Center for Theoretical Physics Clarendon Laboratory University of Oxford OxfordOX1 3PU United Kingdom Department of Physics and Astronomy CUNY College of Staten Island Staten IslandNY10314 United States Physics Program and Initiative for the Theoretical Sciences Graduate Center CUNY New YorkNY10016 United States

We study nonlinear response in quantum systems near strong-randomness critical points. Nonlinear dynamical probes, such as 2D coherent spectroscopy, can diagnose the nearly localized character of excitations in such systems. We focus on the random transverse-field Ising model and derive exact results for nonlinear response, from which we extract information about critical behavior that is absent in linear response. Our analysis incorporates realistic channels for dissipation in random magnets;we present exact scaling forms for the resulting distribution functions of relaxation times. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum optics

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The variability patterns of the TeV blazar PG 1553+113 from a decade of MAGIC and multi-band observations

arXiv

引用

arXiv 2024年

作者： Abe, H. Abe, S. Abhir, J. Acciari, V.A. Agudo, I. Aniello, T. Ansoldi, S. Antonelli, L.A. Engels, A. Arbet Arcaro, C. Artero, M. Asano, K. Baack, D. Babić, A. Baquero, A. de Almeida, U. Barres Batković, I. Baxter, J. González, J. Becerra Bernardini, E. Bernete, J. Berti, A. Besenrieder, J. Bigongiari, C. Biland, A. Blanch, O. Bonnoli, G. Bošnjak, Ž. Burelli, I. Busetto, G. Campoy-Ordaz, A. Carosi, A. Carosi, R. Carretero-Castrillo, M. Castro-Tirado, A.J. Chai, Y. Cifuentes, A. Cikota, S. Colombo, E. Contreras, J.L. Cortina, J. Covino, S. D’Amico, G. D’Elia, V. Da Vela, P. Dazzi, F. De Angelis, A. De Lotto, B. Del Popolo, A. Delfino, M. Delgado, J. Mendez, C. Delgado Depaoli, D. Di Pierro, F. Di Venere, L. Prester, D. Dominis Donini, A. Dorner, D. Doro, M. Elsaesser, D. Emery, G. Escudero, J. Farin͂a, L. Fattorini, A. Foffano, L. Font, L. Fukami, S. Fukazawa, Y. López, R.J. García Gasparyan, S. Gaug, M. Paiva, J.G. Giesbrecht Giglietto, N. Giordano, F. Gliwny, P. Grau, R. Green, J.G. Hadasch, D. Hahn, A. Heckmann, L. Herrera, J. Hovatta, T. Hrupec, D. Hütten, M. Imazawa, R. Inada, T. Iotov, R. Ishio, K. Martínez, I. Jiménez Jormanainen, J. Kerszberg, D. Kluge, G.W. Kobayashi, Y. Kouch, P.M. Kubo, H. Kushida, J. Lezáun, M. Láinez Lamastra, A. Leone, F. Lindfors, E. Liodakis, I. Lombardi, S. Longo, F. López-Moya, M. López-Oramas, A. Loporchio, S. Lorini, A. Fraga, B. Machado de Oliveira Majumdar, P. Makariev, M. Maneva, G. Mang, N. Manganaro, M. Mannheim, K. Mariotti, M. Martínez, M. Martínez-Chicharro, M. Mas-Aguilar, A. Mazin, D. Menchiari, S. Mender, S. Miceli, D. Miener, T. Miranda, J.M. Mirzoyan, R. González, M. Molero Molina, E. Mondal, H.A. Moralejo, A. Morcuende, D. Nakamori, T. Nanci, C. Neustroev, V. Nigro, C. Nikolić, L. Nilsson, K. Nishijima, K. Ekoume, T. Njoh Noda, K. Nozaki, S. Ohtani, Y. Okumura, A. Otero-Santos, J. Paiano, S. Palatiello, M. Paneque, D. Paoletti, R. Paredes, J.M. Pavlović, D. Persic, M. Pihet, M. Pirola, G. The University of Tokyo Chiba Kashiwa277-8582 Japan ETH Zürich ZürichCH-8093 Switzerland Instituto de Astrofísica de Canarias Dpto. de Astrofísica Universidad de La Laguna Tenerife La LagunaE-38200 Spain Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n Granada18008 Spain RomeI-00136 Italy Università di Udine INFN Trieste UdineI-33100 Italy Max-Planck-Institut für Physik MünchenD-80805 Germany Università di Padova INFN PadovaI-35131 Italy Bellaterra BarcelonaE-08193 Spain Technische Universität Dortmund DortmundD-44221 Germany Zagreb10000 Croatia IPARCOS Institute EMFTEL Department Universidad Complutense de Madrid MadridE-28040 Spain URCA RJ Rio de Janeiro22290-180 Brazil Centro de Investigaciones Energéticas Medioambientales y Tecnológicas MadridE-28040 Spain Departament de Física CERES-IEEC Universitat Autònoma de Barcelona BellaterraE-08193 Spain Università di Pisa INFN Pisa PisaI-56126 Italy Universitat de Barcelona ICCUB IEEC-UB BarcelonaE-08028 Spain Department for Physics and Technology University of Bergen Norway INFN MAGIC Group INFN Sezione di Catania Dipartimento di Fisica e Astronomia University of Catania CataniaI-95123 Italy INFN MAGIC Group INFN Sezione di Torino Università degli Studi di Torino TorinoI-10125 Italy INFN MAGIC Group INFN Sezione di Bari Dipartimento Interateneo di Fisica dell’Università e del Politecnico di Bari BariI-70125 Italy Croatian MAGIC Group University of Rijeka Faculty of Physics Rijeka51000 Croatia University of Geneva Chemin d’Ecogia 16 VersoixCH-1290 Switzerland Japanese MAGIC Group: Physics Program Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima739-8526 Japan Armenian MAGIC Group: ICRANet-Armenia Yerevan0019 Armenia University of Lodz Faculty of Physics and Applied Informatics Department of Astrophysics Lodz90-236 Poland Croatian MAGIC Group Josip Juraj Strossmayer University of Osijek Department

PG 1553+113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high-energy (VHE;>100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required. Copyright © 2024, The Authors. All rights reserved.

关键词： Gamma rays

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The 230 GHz Variability of Numerical Models of Sagittarius A* I. Parameter Surveys on Varying Ion-electron Temperature Ratios Under Strongly Magnetized Conditions

arXiv

引用

arXiv 2023年

作者： Chan, Ho-Sang Chan, Chi-Kwan Prather, Ben S. Wong, George N. Gammie, Charles Department of Physics Institute of Theoretical Physics The Chinese University of Hong Kong N.T. Shatin Hong Kong JILA University of Colorado National Institute of Standards and Technology 440 UCB BoulderCO80309-0440 United States Department of Astrophysical and Planetary Sciences University of Colorado 391 UCB BoulderCO80309 United States Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Avenue TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Avenue TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 North Santa Rita TucsonAZ85721 United States Los Alamos National Lab Los AlamosNM87545 United States School of Natural Sciences Institute for Advanced Study 1 Einstein Drive PrincetonNJ08540 United States Princeton Gravity Initiative Princeton University PrincetonNJ08544 United States Department of Physics University of Illinois at Urbana-Champaign 1110 West Green Street UrbanaIL61801 United States Department of Astronomy University of Illinois at Urbana-Champaign 1002 West Green Street UrbanaIL61801 United States NCSA University of Illinois at Urbana-Champaign 1205 W. Clark St. UrbanaIL61801 United States Illinois Center for the Advanced Study of the Universe University of Illinois at Urbana-Champaign 1110 West Green St. UrbanaIL61801 United States

The 230 GHz lightcurves of Sagittarius A* (Sgr A*) predicted by general relativistic magnetohydrodynamics (GRMHD) and ray-tracing (GRRT) models in Event Horizon Telescope Collaboration et al. (2022) have higher variability M∆T compared to observations. In this series of papers, we explore the origin of such large brightness variability. In this first paper, we performed large GRRT parameter surveys that span from the optically thin to the optically thick regimes, covering the ion-electron temperature ratio under strongly magnetized conditions, RLow, from 1 to 60. We find that increasing RLow can lead to either an increase or a reduction in M∆T depending on other model parameters, making it consistent with the observed variability of Sgr A* in some cases. Our analysis of GRRT image snapshots finds that the major contribution to the large M∆T for the RLow = 1 models comes from the photon rings. However, secondary contributions from the accretion flow are also visible depending on the spin parameter. Our work demonstrates the importance of the electron temperature used for modelling radiatively inefficient accretion flows and places new constraints on the ion-electron temperature ratio. A more in-depth analysis for understanding the dependencies of M∆T on RLow will be performed in subsequent papers. © 2023, CC BY.

关键词： Black holes

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Bloch-Grüneisen temperature and universal scaling of normalized resistivity in doped graphene revisited

arXiv

引用

arXiv 2020年

作者： van Nguyen, Khoe Chang, Yia-Chung Research Center for Applied Sciences Academia Sinica Taipei115 Taiwan Molecular Science and Technology Taiwan International Graduate Program Academia Sinica Taipei115 Taiwan Department of Physics National Central University Chungli320 Taiwan Department of Physics National Cheng-Kung University Tainan701 Taiwan

In this work, we resolved some controversial issues on the Bloch-Grüneisen (BG) temperature in doped graphene via analytical and numerical calculations based on full inelastic electron-acoustic-phonon (EAP) scattering rate and various approximation schemes. Analytic results for BG temperature obtained by semi-inelastic (SI) approximation (which gives scattering rates in excellent agreement with the full inelastic scattering rates) are compared with those obtained by quasi-elastic (QE) approximation and the commonly adopted value of ΘLAF = 2~vLAkF/kB. It is found that the commonly adopted BG temperature in graphene (ΘLAF ) is about 5 times larger than the value obtained by the QE approximation and about 2.5 times larger than that by the SI approximation, when using the crossing-point temperature where low-temperature and high-temperature limits of the resistivity meet (criterium 1). The corrected analytic relation based on SI approximation agrees extremely well with the transition temperatures determined by fitting the the low- and high-T behavior of available experimental data of graphene's resistivity. We also introduce a way to determine the BG temperature including the full inelastic EAP scattering rate and the deviation of electron energy from the chemical potential (µ) numerically by finding the maximum of ∂ρ(µ,T)/∂T (criterium 2). It is found that the BG temperature determined by the full numerical calculation with criterium 2 falls between the values obtained analytically via the SI appoximation with criterium 1 (ΘBG,1) and criterium 2 (ΘBG,2 ≈ 1.35ΘBG,1) but neglecting the contribution of electron energies away from µ. Using the analytic expression of ΘBG,1 we can prove that the normalized resistivity defined as R1 = ρ(µ,T)/ρ(µ,ΘBG,1) plotted as a function of (T/ΘBG,1) is independent of the carrier density. Applying our results to the experimental data extracted from [Phys. Rev. Lett. 105, 256805 (2010)] shows a universal scaling behavior, which is different

关键词： Graphene

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Sensing the local magnetic environment through optically active defects in a layered magnetic semiconductor

arXiv

引用

arXiv 2022年

作者： Klein, Julian Song, Zhigang Pingault, Benjamin Dirnberger, Florian Chi, Hang Curtis, Jonathan B. Dana, Rami Bushati, Rezlind Quan, Jiamin Dekanovsky, Lukas Sofer, Zdenek Alù, Andrea Menon, Vinod M. Moodera, Jagadeesh S. Lončar, Marko Narang, Prineha Ross, Frances M. Department of Materials Science and Engineering Massachusetts Institute of Technology CambridgeMA02139 United States John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA United States College of Letters and Sciences UCLA Los AngelesCA90095 United States QuTech Delft University of Technology Delft2600 GA Netherlands Department of Physics City College of New York New YorkNY10031 United States Francis Bitter Magnet Laboratory Plasma Science and Fusion Center Massachusetts Institute of Technology CambridgeMA02139 United States U.S. Army CCDC Army Research Laboratory AdelphiMD20783 United States Department of Physics The Graduate Center City University of New York New YorkNY10016 United States Department of Electrical and Computer Engineering The University of Texas at Austin AustinTX78712 United States Photonics Initiative CUNY Advanced Science Research Center New YorkNY10031 United States Department of Electrical Engineering City College of the City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10026 United States Department of Inorganic Chemistry University of Chemistry and Technology Prague Technická 5 Prague 6166 28 Czech Republic Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States

Atomic-level defects in van der Waals (vdW) materials are essential building blocks for quantum technologies and quantum sensing applications. The layered magnetic semiconductor CrSBr is an outstanding candidate for exploring optically active defects owing to a direct gap in addition to a rich magnetic phase diagram including a recently hypothesized defect-induced magnetic order at low temperature. Here, we show optically active defects in CrSBr that are probes of the local magnetic environment. We observe spectrally narrow (1 meV) defect emission in CrSBr that is correlated with both the bulk magnetic order and an additional low temperature defect-induced magnetic order. We elucidate the origin of this magnetic order in the context of local and non-local exchange coupling effects. Our work establishes vdW magnets like CrSBr as an exceptional platform to optically study defects that are correlated with the magnetic lattice. We anticipate that controlled defect creation allows for tailor-made complex magnetic textures and phases with the unique ingredient of direct optical access. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnetic semiconductors

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Magnetism of fullerene C60compared with graphene molecule by DFT calculation, laboratory experiment and astronomical observation

arXiv

引用

arXiv 2021年

作者： Ota, Norio Li, Aigen Nemes, Laszlo Otsuka, Masaaki Graduate School of Pure and Applied Sciences University of Tsukuba 1-1-1 Tennodai Ibaraki Tsukuba305-8571 Japan Department of Physics and Astronomy University of Missouri ColumbiaMO65211 United States Research Center for Natural Sciences Ötvös Lóránd Research Network Budapest1519 Hungary Okayama Observatory Kyoto University Asakuchi Okayama719-0232 Japan

Magnetismof fullerene C60was studied by three methods of the density functional theory (DFT) calculation, laboratory experiment and astronomical *** revealed that the most stable spin state was non-magnetic one of Sz=0/*** is contrary to our recent study on void induced graphene molecules of C23and C53to be magnetic one of Sz=2/*** combined model suggested that two up-spin at every carbon pentagon ring may cancel each other to bring Sz=0/2. Similar cancelation may occur on C60. Molecular vibrational infrared spectrum of C60show four major bands, which coincide with gas-phase laboratory experiment, also with astronomically observed one of carbon rich planetary nebula Tc1 and Lin49. However, there remain many unidentified bands on astronomical one. We supposed multiple voids on graphene sheet, which may create both C60and complex graphene molecules. It was revealed that spectrum of two voids induced graphene molecule coincident well with major astronomical bands. Simple sum of C60andgraphene moleculescould successfully reproduce astronomical bands in detail. © 2021, CC BY.

关键词： Density functional theory

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Morphological, optical and antibacterial study of green synthesized silver nanoparticles via Vernonia amygdalina

引用

Materials Today: Proceedings 2021年 36卷 199-203页

作者： Samson O. Aisida Kenneth Ugwu Paul A. Akpa Assumpta C. Nwanya Paul M. Ejikeme S. Botha Ishaq Ahmad Fabian I. Ezema Department of Physics and Astronomy University of Nigeria Nsukka Nigeria National Centre for Physics Quaid-i-Azam University Campus Islamabad 44000 Pakistan Nanosciences African Network (NANOAFNET) iThemba LABS-National Research South Africa UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology College of Graduate Studies University of South Africa (UNISA) Muckleneuk Ridge P.O. Box 392 Pretoria South Africa Department of Microbiology University of Nigeria Nsukka Nigeria Department of Pharmaceutics University of Nigeria Nsukka Nigeria Department of Pure and Industrial Chemistry University of Nigeria Nsukka Nigeria Miscroscopy Unit University of Western Cape South Africa NPU-NCP Joint International Research Center on Advanced Nanomaterials and Defects Engineering Northwestern Polytechnic University Xi'an 710072 China Department of Physics Faculty of Natural and Applied Sciences Coal City University Enugu Nigeria

Green synthesis of silver nanoparticles (AgNPs) through a fresh leave of Vernonia amygdalina (FLVA) inherent in flavonoids, tannins and phenols phytochemical as a capping and reducing agent is demonstrated in this work. The antibacterial activities of the formulated AgNPs were studied. The synthesized AgNPs were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray dispersive spectroscopy (XRD), UV–Visible spectroscopy and Fourier transform infrared spectroscopy (FT-IR) analysis. The UV–visible confirm the formation of AgNPs with surface plasmon resonance (SPR) absorbance peak between 430 and 465 nm. The TEM analysis gave a spherical morphology with particle size ranged between 2 and 10 nm. The XRD gave a face-centered cubic phase with the crystalline structure of AgNPs. To our knowledge, the antibacterial activities of AgNPs have been studied in details but the green synthesis of AgNPs via FLVA against Coliform and Staphylococcus aureus bacterial strains has not been reported in the literature. It is noteworthy that the formulated AgNPs show effective susceptibility to the AgNPs against the bacterial strains compared with Gentamicin. Hence, the obtained AgNPs via facile and innocuous synthesis, demonstrated good therapeutic agent against human pathogens strains due to its non-toxicity and facile method of synthesis.

关键词： Green-synthesis Antibacterial Silver nanoparticles Vernonia amygdalina

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EMPRESS. XIV. Strong High Ionization Lines of Young Galaxies at z = 0 − 8: Ionizing Spectra Consistent with the Intermediate Mass Black Holes with MBH ∼ 103 − 106 M☉

arXiv

引用

arXiv 2023年

作者： Hatano, Shun Ouchi, Masami Umeda, Hiroya Nakajima, Kimihiko Kawaguchi, Toshihiro Isobe, Yuki Aoyama, Shohei Watanabe, Kuria Harikane, Yuichi Kusakabe, Haruka Matsumoto, Akinori Moriya, Takashi J. Nishigaki, Moka Ono, Yoshiaki Onodera, Masato Sugahara, Yuma Suzuki, Akihiro Xu, Yi Zhang, Yechi National Astronomical Observatory of Japan Osawa 2-21-1 Mitaka Tokyo181-8588 Japan Department of Astronomical Science The Graduate University for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Institute for Cosmic Ray Research The University of Tokyo 5-1-5 Kashiwanoha Chiba Kashiwa277-8582 Japan Astronomical Science Program Graduate Institute for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan University of Tokyo Chiba Kashiwa277-8583 Japan Department of Physics Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan Department of Economics Management and Information Science Onomichi City University Hisayamada 1600-2 Onomichi Hiroshima722-8506 Japan Institute of Management and Information Technologies Chiba University 1-33 Yayoi-cho Inage-ward Chiba263-8522 Japan Observatoire de Genéve Université de Genéve 51 Ch. des Maillettes Versoix1290 Switzerland School of Physics and Astronomy Faculty of Science Monash University ClaytonVIC3800 Australia 650 North A’ohoku Place HiloHI96720 United States Waseda Research Institute for Science and Engineering Faculty of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku Tokyo169-8555 Japan Research Center for the Early Universe The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan Department of Astronomy Graduate School of Science the University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan

We present ionizing spectra estimated at 13.6–100 eV for ten dwarf galaxies with strong high ionization lines of He iiλ4686 and [Ne v]λ3426 ([Ne iv]λ2424) at z = 0 (z = 8) that are identified in our Keck/LRIS spectroscopy and the literature (the JWST ERO program). With the flux ratios of these high ionization lines and > 10 low-ionization lines of hydrogen, helium, oxygen, neon, and sulfur, we determine ionizing spectra consisting of stellar and non-thermal power-law radiation by photoionization modeling with free parameters of nebular properties including metallicity and ionization parameter, cancelling out abundance ratio differences. We find that all of the observed flux ratios are well reproduced by the photoinization models with the power law index αEUV of αEUV ∼ (−1) − 0 and the luminosity LEUV of LEUV ∼ 1040 − 1042 erg s−1 at ∼ 55 − 100 eV for six galaxies, while four galaxies include large systematics in αEUV caused by stellar radiation contamination. We then compare αEUV and LEUV of these six galaxies with those predicted by the black hole (BH) accretion disk models, and find that αEUV and LEUV are similar to those of the intermediate mass black holes (IMBHs) in BH accretion disk models albeit with possibilities of the other scenarios. Confirming these results with a known IMBH having a mass MBH of MBH = 105.75 M☉, we find that four local galaxies and one z = 7.665 galaxy have ionizing spectra consistent with those of IMBHs with MBH ∼ 103 − 105 M☉. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

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Layer-dependent optically-induced spin polarization in InSe

arXiv

引用

arXiv 2022年

作者： Nelson, Jovan Stanev, Teodor K. Lebedev, Dmitry LaMountain, Trevor Tyler Gish, J. Zeng, Hongfei Shin, Hyeondeok Heinonen, Olle Watanabe, Kenji Taniguchi, Takashi Hersam, Mark C. Stern, Nathaniel P. Applied Physics Program Northwestern University EvanstonIL60208 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Material Science & Engineering Northwestern University EvanstonIL60208 United States Computational Science Division Argonne National Laboratory LemontIL60439 United States Material Science Division Argonne National Laboratory LemontIL60439 United States Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

Optical control of spin in semiconductors has been pioneered using nanostructures of III-V and II-VI semiconductors, but the emergence of two-dimensional van der Waals materials offers an alternative low-dimensional platform for spintronic phenomena. Indium selenide (InSe), a group-III monochalcogenide van der Waals material, has shown promise for opto-electronics due to its high electron mobility, tunable direct bandgap, and quantum transport. In addition to these confirmed properties, there are predictions of spin-dependent optical selection rules suggesting potential for all-optical excitation and control of spin in a two-dimensional layered material. Despite these predictions, layer-dependent optical spin phenomena in InSe have yet to be explored. Here, we present measurements of layer-dependent optical spin dynamics in few-layer and bulk InSe. Polarized photo-luminescence reveals layer-dependent optical orientation of spin, thereby demonstrating the optical selection rules in few-layer InSe. Spin dynamics are also studied in many-layer InSe using time-resolved Kerr rotation spectroscopy. By applying out-of-plane and in-plane static magnetic fields for polarized emission measurements and Kerr measurements, respectively, the g-factor for InSe was extracted. Further investigations are done by calculating precession values using a k·p model, which is supported by ab-initio density functional theory. Comparison of predicted precession rates with experimental measurements highlights the importance of excitonic effects in InSe for understanding spin dynamics. Optical orientation of spin is an important prerequisite for opto-spintronic phenomena and devices, and these first demonstrations of layer-dependent optical excitation of spins in InSe lay the foundation for combining layer-dependent spin properties with advantageous electronic properties found in this material. Copyright © 2022, The Authors. All rights reserved.

关键词： Spin dynamics

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