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arXiv 2021年

作者： Chumak, Andrii V. Kabos, P. Wu, M. Abert, C. Adelmann, C. Adeyeye, A. Åkerman, J. Aliev, F.G. Anane, A. Awad, A. Back, C.H. Barman, A. Bauer, G.E.W. Becherer, M. Beginin, E.N. Bittencourt, V.A.S.V. Blanter, Y.M. Bortolotti, P. Boventer, I. Bozhko, D.A. Bunyaev, S.A. Carmiggelt, J.J. Cheenikundil, R.R. Ciubotaru, F. Cotofana, S. Csaba, G. Dobrovolskiy, O.V. Dubs, C. Elyasi, M. Fripp, K.G. Fulara, H. Golovchanskiy, I.A. Gonzalez-Ballestero, C. Graczyk, P. Grundler, D. Gruszecki, P. Gubbiotti, G. Guslienko, K. Haldar, A. Hamdioui, S. Hertel, R. Hillebrands, B. Hioki, T. Houshang, A. Hu, C.-M. Huebl, H. Huth, M. Iacocca, E. Jungfleisch, M.B. Kakazei, G.N. Khitun, A. Khymyn, R. Kikkawa, T. Kläui, M. Klein, O. Klos, J.W. Knauer, S. Koraltan, S. Kostylev, M. Krawczyk, M. Krivorotov, I.N. Kruglyak, V.V. Lachance-Quirion, D. Ladak, S. Lebrun, R. Li, Y. Lindner, M. Macêdo, R. Mayr, S. Melkov, G.A. Mieszczak, S. Nakamura, Y. Nembach, H.T. Nikitin, A.A. Nikitov, S.A. Novosad, V. Otalora, J.A. Otani, Y. Papp, A. Pigeau, B. Pirro, P. Porod, W. Porrati, F. Qin, H. Rana, B. Reimann, T. Riente, F. Romero-Isart, O. Ross, A. Sadovnikov, A.V. Safin, A.R. Saitoh, E. Schmidt, G. Schultheiss, H. Schultheiss, K. Serga, A.A. Sharma, S. Shaw, J.M. Suess, D. Surzhenko, O. Szulc, K. Taniguchi, T. Urbánek, M. Usami, K. Ustinov, A.B. van der Sar, T. van Dijken, S. Vasyuchka, V.I. Verba, R. Viola Kusminskiy, S. Wang, Q. Weides, M. Weiler, M. Wintz, S. Wolski, S.P. Zhang, X. Faculty of Physics University of Vienna Boltzmanngasse 5 ViennaA-1090 Austria National Institute of Standards and Technology BoulderCO80305 United States Department of Physics Colorado State University Fort CollinsCO80523 United States Research Platform MMM Mathematics-Magnetism-Materials University of Vienna Oskar-Morgenstern-Platz 1 Vienna1090 Austria Imec Leuven3001 Belgium Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom Department of Physics University of Gothenburg Gothenburg412 96 Sweden Universidad Autónoma de Madrid Madrid28049 Spain Unité Mixte de Physique CNRS Thales Université Paris Saclay Palaiseau91767 France Department of Physics Technical University of Munich Garching85748 Germany Department of Condensed Matter Physics and Material Sciences S N Bose National Centre for Basic Sciences Salt Lake Kolkata700106 India Advanced Institute for Materials Research Tohoku University Sendai980-8577 Japan Zernike Institute for Advanced Materials University of Groningen Netherlands Department of Electrical and Computer Engineering Technical University of Munich Munich80333 Germany Laboratory of Magnetic Metamaterials Saratov State University Saratov410012 Russia Max Planck Institute for the Science of Light Erlangen91058 Germany Department of Quantum Nanoscience Kavli Institute of Nanoscience Delft University of Technology Delft2628 CJ Netherlands Department of Physics and Energy Science University of Colorado Colorado Springs Colorado SpringsCO80918 United States Departamento de Física e Astronomia Universidade do Porto Porto4169-007 Portugal Institut de Physique et Chimie des Matériaux de Strasbourg CNRS Université de Strasbourg StrasbourgF-67000 France Department of Quantum and Computer Engineering Delft University of Technology Delft2628 CD Netherlands Faculty for Information Technology and Bionics Pazmany Peter Catholic University Prater u. 50/A BudapestH-1083 Hungary INNOVENT e.V.

Magnonics is a field of science that addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operations in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of the current challenges and the outlook of the further development of the research directions. © 2021, CC BY.

关键词： Spin waves

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Néel-type skyrmion in WTe2/Fe3GeTe2 van der Waals heterostructure

arXiv

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arXiv 2019年

作者： Wu, Yingying Zhang, Senfu Zhang, Junwei Wang, Wei Zhu, Yang Lin Hu, Jin Wong, Kin Fang, Chi Wan, Caihua Han, Xiufeng Shao, Qiming Taniguchi, Takashi Watanabe, Kenji Mao, Zhiqiang Zhang, Xixiang Wang, Kang L. Department of Electrical and Computer Engineering University of California - Los Angeles Los AngelesCA90095 United States Physical Science and Engineering Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia Key Laboratory of Flexible Electronics Institute of Advanced Materials Jiangsu National Synergetic Innovation Center for Advanced Materials Nanjing Tech University Nanjing211816 China Department of Physics Pennsylvania State University University ParkPA16802 United States Department of Physics University of Arkansas FayettevilleAR72701 United States Institute of Physics Chinese Academy of Sciences Beijing100190 China National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

The promise of high-density and low-energy-consumption devices motivates the search for layered structures that stabilize chiral spin textures such as topologically protected skyrmions. Recently discovered long-range intrinsic magnetic orders in the two-dimentional van der Waals materials provide a new platform. Here we demonstrate the Dzyalosinskii-Moriya interaction and Néel-type skyrmions are induced at the WTe2/Fe3GeTe2 interface. Fe3GeTe2 is a ferromagnetic material with strong perpendicular magnetic anisotropy. We demonstrate that the strong spin-orbit interaction in 1T’-WTe2 does induce a large interfacial Dzyalosinskii-Moriya interaction at the interface with Fe3GeTe2 due to the inversion symmetry breaking to stabilize skyrmions. Transport measurements show the topological Hall effect in this heterostructure for temperatures below 100 K. Furthermore, Lorentz transmission electron microscopy is used to directly image Néel-type skyrmions along with aligned and stripe-like domain structure. This interfacial coupling induced Dzyalosinskii-Moriya interaction is estimated to have a large energy of 1.0 mJ/m2, which can stabilize the Néel-type skyrmions in this heterostructure. This work paves a path towards the skyrmionic devices based on van der Waals heterostructures. Copyright © 2019, The Authors. All rights reserved.

关键词： Germanium alloys

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Dynamics of topological solitons, knotted streamlines, and transport of cargo in liquid crystals

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Physical Review E 2018年第5期97卷 052701-052701页

作者： Hayley R. O. Sohn Paul J. Ackerman Timothy J. Boyle Ghadah H. Sheetah Bengt Fornberg Ivan I. Smalyukh Soft Materials Research Center and Materials Science and Engineering Program University of Colorado Boulder Colorado 80309 USA Department of Physics and Department of Electrical Computer and Energy Engineering University of Colorado Boulder Colorado 80309 USA Department of Applied Mathematics University of Colorado Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA

Active colloids and liquid crystals are capable of locally converting the macroscopically supplied energy into directional motion and promise a host of new applications, ranging from drug delivery to cargo transport at the mesoscale. Here we uncover how topological solitons in liquid crystals can locally transform electric energy to translational motion and allow for the transport of cargo along directions dependent on frequency of the applied electric field. By combining polarized optical video microscopy and numerical modeling that reproduces both the equilibrium structures of solitons and their temporal evolution in applied fields, we uncover the physical underpinnings behind this reconfigurable motion and study how it depends on the structure and topology of solitons. We show that, unexpectedly, the directional motion of solitons with and without the cargo arises mainly from the asymmetry in rotational dynamics of molecular ordering in liquid crystal rather than from the asymmetry of fluid flows, as in conventional active soft matter systems.

关键词： Chirality Topological defects Active nematics Cholesteric liquid crystals Nanoparticles Nematic liquid crystals Soft colloids Solitons

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2D Metamaterials: Designing Mechanical Metamaterials with Kirigami-Inspired, Hierarchical Constructions for Giant Positive and Negative Thermal Expansion (Adv. Mater. 3/2021)

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Advanced materials 2021年第3期33卷

作者： Xiaogang Guo Xiaoyue Ni Jiahong Li Hang Zhang Fan Zhang Huabin Yu Jun Wu Yun Bai Hongshuai Lei Yonggang Huang John A. Rogers Yihui Zhang AML Department of Engineering Mechanics Center for Flexible Electronics Technology Tsinghua University Beijing 100084 China Institute of Advanced Structure Technology Beijing Institute of Technology Beijing 100081 China Center for Bio-Integrated Electronics Northwestern University Evanston IL 60208 USA Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA Department of Mechanical Engineering Northwestern University Evanston IL 60208 USA Department of Civil and Environmental Engineering Northwestern University Evanston IL 60208 USA Simpson Querrey Institute Northwestern University Chicago IL 60611 USA Department of Biomedical Engineering Northwestern University Evanston IL 60208 USA Department of Chemistry Northwestern University Evanston IL 60208 USA Department of Electrical and Computer Engineering Northwestern University Evanston IL 60208 USA Department of Neurological Surgery Northwestern University Evanston IL 60208 USA

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electrical Stimulation in Combating Pressure Ulcer for Immobilize Subjects: A Conceptual Framework

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Journal of Physics: Conference Series 2019年第1期1372卷

作者： Amelia Wong Azman Rashidah Funke Olanrewaju Fajingbesi, Fawwaz Eniola Ahmad, Zuraida Yasir Mohd Mustafah Nur Azah Hamzaid Department of Electrical and Computer Engineering Department of Electrical and Computer Engineering Department of Physics Electronics and Earth Science Fountain University Osogbo Nigeria Department of Manufacturing and Materials Engineering Department of Mechatronics Engineering International Islamic University Malaysia Department of Biomedical Engineering Faculty of Engineering University Malaya

A paradigm shift in health system did intensify the need for research on wearable electronics. There are numerous reasons that could lead to skin ulcers. The most common are lesion due to constant pressure, incontinence control, excessive humidity and postural changes. Over the years, there have been numerous interventions ranging from specific skin treatment, introducing prevention programs as well as to mechanical intervention. On the rise in such clinical rehabilitation program is the use of electrical stimulation (ES) at a therapeutic level, wound care and muscle function restoration. This paper presents a concept development and implementation process of a new pressure ulcer intervention system which can be used for both chairbound and bedridden patients. The concept here is to integrate the use of electrical stimulation, interface pressure mapping and redistribution with antimicrobial protection not only to act as therapeutic but at the same time as a means of prevention of pressure ulcers by improving muscle tone and decreasing atrophy among immobilized subjects.

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Design of a monolithic low-threshold narrow-linewidth cw mid-IR silicon Raman laser

arXiv

引用

arXiv 2018年

作者： Behzadi, Behsan Jain, Ravinder K. Hossein-Zadeh, Mani Center for High Technology Materials and Optical Science and Engineering program Department of Physics and Electrical Engineering University of New Mexico New MexicoNM87131 United States

We present the design and anticipated performance of an optically pumped monolithic all-silicon mid-IR (MIR) Raman laser. For the proposed 3.15 μm cw laser design pumped at a 2.71 μm pump wavelength, we estimate a t... 详细信息

关键词： Pumping (laser)

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Picosecond spin orbit torque switching

arXiv

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arXiv 2019年

作者： Jhuria, Kaushalya Hohlfeld, Julius Pattabi, Akshay Martin, Elodie Córdova, Aldo Ygnacio Arriola Shi, Xinping Conte, Roberto Lo Petit-Watelot, Sebastien Rojas-Sanchez, Juan Carlos Malinowski, Gregory Mangin, Stéphane Lemaître, Aristide Hehn, Michel Bokor, Jeffrey Wilson, Richard B. Gorchon, Jon Université de Lorraine CNRS IJL NancyF-54000 France Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA94720 United States Universidad Nacional de Ingeniería Avenida Túpac Amaru 210 Rímac Lima Peru Department of Mechanical Engineering and Materials Science and Engineering Program University of California RiversideCA92521 United States CNRS Université Paris Sud Université Paris-Saclay Palaiseau91120 France Lawrence Berkeley National Laboratory 1 Cyclotron Road BerkeleyCA94720 United States

Reducing energy dissipation while increasing speed in computation and memory is a long-standing challenge for spintronics research1. In the last 20 years, femtosecond lasers have emerged as a tool to control the magnetization in specific magnetic materials at the picosecond timescale2-4. However, the use of ultrafast optics in integrated circuits and memories would require a major paradigm shift. An ultrafast electrical control of the magnetization is far preferable for integrated systems. Here we demonstrate reliable and deterministic control of the out-of-plane magnetization of a 1 nm-thick Co layer with single 6 ps-wide electrical pulses that induce spin orbit torques on the magnetization. We can monitor the ultrafast magnetization dynamics due to the spin orbit torques on sub-picosecond timescales, thus far accessible only by numerical simulations. Due to the short duration of our pulses, we enter a counter-intuitive regime of switching where heat dissipation assists the reversal. Moreover, we estimate a low energy cost to switch the magnetization, projecting to below 1fJ for a (20 nm)3 cell. These experiments prove that spintronic phenomena can be exploited on picosecond time-scales for full magnetic control and should launch a new regime of ultrafast spin torque studies and applications. Copyright © 2019, The Authors. All rights reserved.

关键词： Magnetization

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Mineral detection of neutrinos and dark matter. A whitepaper

引用

Physics of the Dark Universe 2023年 41卷

作者： Baum, Sebastian Stengel, Patrick Abe, Natsue Acevedo, Javier F. Araujo, Gabriela R. Asahara, Yoshihiro Avignone, Frank Balogh, Levente Baudis, Laura Boukhtouchen, Yilda Bramante, Joseph Breur, Pieter Alexander Caccianiga, Lorenzo Capozzi, Francesco Collar, Juan I. Ebadi, Reza Edwards, Thomas Eitel, Klaus Elykov, Alexey Ewing, Rodney C. Freese, Katherine Fung, Audrey Galelli, Claudio Glasmacher, Ulrich A. Gleason, Arianna Hasebe, Noriko Hirose, Shigenobu Horiuchi, Shunsaku Hoshino, Yasushi Huber, Patrick Ido, Yuki Igami, Yohei Ishikawa, Norito Itow, Yoshitaka Kamiyama, Takashi Kato, Takenori Kavanagh, Bradley J. Kawamura, Yoji Kazama, Shingo Kenney, Christopher J. Kilminster, Ben Kouketsu, Yui Kozaka, Yukiko Kurinsky, Noah A. Leybourne, Matthew Lucas, Thalles McDonough, William F. Marshall, Mason C. Mateos, Jose Maria Mathur, Anubhav Michibayashi, Katsuyoshi Mkhonto, Sharlotte Murase, Kohta Naka, Tatsuhiro Oguni, Kenji Rajendran, Surjeet Sakane, Hitoshi Sala, Paola Scholberg, Kate Semenec, Ingrida Shiraishi, Takuya Spitz, Joshua Sun, Kai Suzuki, Katsuhiko Tanin, Erwin H. Vincent, Aaron Vladimirov, Nikita Walsworth, Ronald L. Watanabe, Hiroko Stanford Institute for Theoretical Physics Department of Physics Stanford University Stanford 94305 CA United States Istituto Nazionale di Fisica Nucleare Sezione di Ferrara via Giuseppe Saragat 1 Ferrara I-44122 Italy Mantle Drilling Promotion Office Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kanagawa Yokohama 236-0001 Japan SLAC National Accelerator Laboratory Stanford University 2575 Sand Hill Road Menlo Park 94025 CA United States Department of Physics University of Zurich Winterthurerstrasse 190 Zurich CH-8057 Switzerland Department of Earth and Environmental Sciences Graduate School of Environmental Studies Nagoya University Furo-cho Chikusa-ku Nagoya 464-8601 Japan Department of Physics and Astronomy University of South Carolina Columbia 29208 SC United States Mechanical and Materials Engineering Queen's University 130 Stuart Street Kingston K7L 2V9 ON Canada Department of Physics Engineering Physics and Astronomy Queen's University 64 Bader Lane KingstonOntario K7L 2S8 Canada Perimeter Institute for Theoretical Physics Waterloo N2J 2W9 ON Canada Istituto Nazionale di Fisica Nucleare Sezione di Milano Via Celoria 16 Milan Italy Dipartimento di Scienze Fisiche e Chimiche Università degli Studi dell'Aquila L'Aquila 67100 Italy Department of Physics University of Chicago Chicago 60637 IL United States Department of Physics University of Maryland College Park 20742 MD United States Quantum Technology Center University of Maryland College Park 20742 MD United States The William H. Miller III Department of Physics and Astronomy The Johns Hopkins University Baltimore 21218 MD United States Institute for Astroparticle Physics Karlsruhe Institute of Technology Karlsruhe 76021 Germany Earth and Planetary Sciences Stanford University Stanford 94305-2115 CA United States Texas Center for Cosmology and Astroparticle Physics Weinberg Institute for Theoretical Physics Department of Physics The University of

Minerals are solid state nuclear track detectors — nuclear recoils in a mineral leave latent damage to the crystal structure. Depending on the mineral and its temperature, the damage features are retained in the material from minutes (in low-melting point materials such as salts at a few hundred °C) to timescales much larger than the 4.5Gyr-age of the Solar System (in refractory materials at room temperature). The damage features from the O(50)MeV fission fragments left by spontaneous fission of ²³⁸U and other heavy unstable isotopes have long been used for fission track dating of geological samples. Laboratory studies have demonstrated the readout of defects caused by nuclear recoils with energies as small as O(1)keV. This whitepaper discusses a wide range of possible applications of minerals as detectors for E_R≳O(1)keV nuclear recoils: Using natural minerals, one could use the damage features accumulated over O(10)Myr–O(1)Gyr to measure astrophysical neutrino fluxes (from the Sun, supernovae, or cosmic rays interacting with the atmosphere) as well as search for Dark Matter. Using signals accumulated over months to few-years timescales in laboratory-manufactured minerals, one could measure reactor neutrinos or use them as Dark Matter detectors, potentially with directional sensitivity. Research groups in Europe, Asia, and America have started developing microscopy techniques to read out the O(1)–O(100)nm damage features in crystals left by O(0.1)–O(100)keV nuclear recoils. We report on the status and plans of these programs. The research program towards the realization of such detectors is highly interdisciplinary, combining geoscience, material science, applied and fundamental physics with techniques from quantum information and Artificial Intelligence. © 2023 Elsevier B.V.

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First Constraints on the Epoch of Reionization Using the Non-Gaussianity of the Kinematic Sunyaev-Zel’dovich Effect from the South Pole Telescope and Herschel-SPIRE Observations

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Physical Review Letters 2024年第12期133卷 121004页

作者： S. Raghunathan P. A. R. Ade A. J. Anderson B. Ansarinejad M. Archipley J. E. Austermann L. Balkenhol J. A. Beall K. Benabed A. N. Bender B. A. Benson F. Bianchini L. E. Bleem J. Bock F. R. Bouchet L. Bryant E. Camphuis J. E. Carlstrom T. W. Cecil C. L. Chang P. Chaubal H. C. Chiang P. M. Chichura T.-L. Chou R. Citron A. Coerver T. M. Crawford A. T. Crites A. Cukierman C. Daley K. R. Dibert M. A. Dobbs A. Doussot D. Dutcher W. Everett C. Feng K. R. Ferguson K. Fichman A. Foster S. Galli J. Gallicchio A. E. Gambrel R. W. Gardner F. Ge E. M. George N. Goeckner-Wald R. Gualtieri F. Guidi S. Guns N. Gupta T. de Haan N. W. Halverson E. Hivon G. P. Holder W. L. Holzapfel J. C. Hood J. D. Hrubes A. Hryciuk N. Huang J. Hubmayr K. D. Irwin F. Kéruzoré A. R. Khalife L. Knox M. Korman K. Kornoelje C.-L. Kuo A. T. Lee K. Levy D. Li A. E. Lowitz C. Lu A. Maniyar E. S. Martsen J. J. McMahon F. Menanteau M. Millea J. Montgomery C. Corbett Moran Y. Nakato T. Natoli J. P. Nibarger G. I. Noble V. Novosad Y. Omori S. Padin Z. Pan P. Paschos S. Patil K. A. Phadke K. Prabhu C. Pryke W. Quan M. Rahimi A. Rahlin C. L. Reichardt M. Rouble J. E. Ruhl B. R. Saliwanchik K. K. Schaffer E. Schiappucci C. Sievers G. Smecher J. A. Sobrin A. A. Stark J. Stephen A. Suzuki C. Tandoi K. L. Thompson B. Thorne C. Trendafilova C. Tucker C. Umilta T. Veach J. D. Vieira M. P. Viero Y. Wan G. Wang N. Whitehorn W. L. K. Wu V. Yefremenko M. R. Young J. A. Zebrowski M. Zemcov Center for AstroPhysical Surveys School of Physics and Astronomy Cardiff University Cardiff CF24 3YB United Kingdom Fermi National Accelerator Laboratory MS209 P.O. Box 500 Batavia Illinois 60510 USA Kavli Institute for Cosmological Physics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Department of Astronomy and Astrophysics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA School of Physics University of Melbourne Parkville Victoria 3010 Australia Department of Astronomy University of Illinois Urbana-Champaign 1002 West Green Street Urbana Illinois 61801 USA NIST Quantum Devices Group 325 Broadway Mailcode 817.03 Boulder Colorado 80305 USA Department of Physics University of Colorado Boulder Colorado 80309 USA Institut d’Astrophysique de Paris UMR 7095 CNRS and Sorbonne Université 98 bis boulevard Arago 75014 Paris France High-Energy Physics Division Argonne National Laboratory 9700 South Cass Avenue Lemont Illinois 60439 USA Kavli Institute for Particle Astrophysics and Cosmology Stanford University 452 Lomita Mall Stanford California 94305 USA Department of Physics Stanford University 382 Via Pueblo Mall Stanford California 94305 USA SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park California 94025 USA California Institute of Technology Pasadena California 91125 USA Jet Propulsion Laboratory California Institute of Technology Pasadena California 91109 USA Enrico Fermi Institute University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Department of Physics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Department of Physics and McGill Space Institute McGill University 3600 Rue University Montreal Quebec H3A 2T8 Canada School of Mathematics Statistics and Computer Science University of KwaZulu-Natal Durban South Africa University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Department of Physics

We report results from an analysis aimed at detecting the trispectrum of the kinematic Sunyaev-Zel’dovich (kSZ) effect by combining data from the South Pole Telescope (SPT) and Herschel-SPIRE experiments over a 100 deg2 field. The SPT observations combine data from the previous and current surveys, namely SPTpol and SPT-3G, to achieve depths of 4.5, 3, and 16 μK−arcmin in bands centered at 95, 150, and 220 GHz. For SPIRE, we include data from the 600 and 857 GHz bands. We reconstruct the velocity-induced large-scale correlation of the small-scale kSZ signal with a quadratic estimator that uses two cosmic microwave background (CMB) temperature maps, constructed by optimally combining data from all the frequency bands. We reject the null hypothesis of a zero trispectrum at 10.3σ level. However, the measured trispectrum contains contributions from both the kSZ and other undesired components, such as CMB lensing and astrophysical foregrounds, with kSZ being sub-dominant. We use the agora simulations to estimate the expected signal from CMB lensing and astrophysical foregrounds. After accounting for the contributions from CMB lensing and foreground signals, we do not detect an excess kSZ-only trispectrum and use this nondetection to set constraints on reionization. By applying a prior based on observations of the Gunn-Peterson trough, we obtain an upper limit on the duration of reionization of Δzre,50<4.5 (95% confidence level). We find these constraints are fairly robust to foregrounds assumptions. This trispectrum measurement is independent of, but consistent with, Planck’s optical depth measurement. This result is the first constraint on the epoch of reionization using the non-Gaussian nature of the kSZ signal.

关键词： Cosmic microwave background Evolution of the Universe Formation & evolution of stars & galaxies

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Real-space observation of skyrmion clusters with mutually orthogonal skyrmion tubes

arXiv

引用

arXiv 2019年

作者： Sohn, Hayley R.O. Vlasov, Sergei M. Uzdin, Valeriy M. Leonov, Andrey O. Smalyukh, Ivan I. Soft Materials Research Center and Materials Science and Engineering Program University of Colorado BoulderCO80309 United States ITMO University Saint Petersburg197101 Russia Department of Physics St. Petersburg State University St. Petersburg198504 Russia Chirality Research Center Hiroshima University Higashi-HiroshimaHiroshima739-8526 Japan Department of Chemistry Faculty of Science Hiroshima University Kagamiyama Higashi HiroshimaHiroshima739-8526 Japan IFW Dresden Postfach 270016 DresdenD-01171 Germany Department of Physics Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

We report the discovery and direct visualization of skyrmion clusters with mutually-orthogonal orientations of constituent isolated skyrmions in chiral liquid crystals and ferromagnets. We show that the nascent conical state underlies attracting inter-skyrmion potential, whereas an encompassing homogeneous state leads to the repulsive skyrmion-skyrmion interaction. The crossover between different regimes of skyrmion interaction could be identified upon changing layer thickness and/or the surface anchoring. We develop a phenomenological theory describing two types of skyrmions and the underlying mechanisms of their interaction. We show that isolated horizontal skyrmions with the same polarity may approach a vertical isolated skyrmion from both sides and thus constitute two energetically-different configurations which are also observed experimentally. In an extreme regime of mutual attraction, the skyrmions wind around each other forming compact superstructures with undulations. We also indicate that our numerical simulations on skyrmion clusters are valid in a parameter range corresponding to the A-phase region of cubic helimagnets. Copyright © 2019, The Authors. All rights reserved.

关键词： Liquid crystals

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