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arXiv 2023年

作者： Abe, S. Eizuka, M. Futagi, S. Gando, A. Gando, Y. Goto, S. Hachiya, T. Hata, K. Hosokawa, K. Ichimura, K. Ieki, S. Ikeda, H. Inoue, K. Ishidoshiro, K. Kamei, Y. Kawada, N. Kishimoto, Y. Koga, M. Kurasawa, M. Mitsui, T. Miyake, H. Morita, D. Nakahata, T. Nakajima, R. Nakamura, K. Nakamura, R. Nakane, J. Ozaki, H. Sakai, T. Shimizu, I. Shirai, J. Shiraishi, K. Shoji, R. Suzuki, A. Takeuchi, A. Tamae, K. Watanabe, H. Watanabe, K. Obara, S. Yoshida, S. Umehara, S. Fushimi, K. Kotera, K. Urano, Y. Ichikawa, A. Berger, B.E. Fujikawa, B.K. Learned, J.G. Maricic, J. Axani, S.N. Fu, Z. Smolsky, J. Winslow, L.A. Efremenko, Y. Karwowski, H.J. Markoff, D.M. Tornow, W. Dell'Oro, S. O'Donnell, T. Detwiler, J.A. Enomoto, S. Decowski, M.P. Weerman, K.M. Grant, C. Li, A. Song, H. Research Center for Neutrino Science Tohoku University Sendai980-8578 Japan Department of Human Science Obihiro University of Agriculture and Veterinary Medicine Obihiro080-8555 Japan The University of Tokyo Institutes for Advanced Study Chiba Kashiwa277-8583 Japan Graduate Program on Physics for the Universe Tohoku University Sendai980-8578 Japan Frontier Research Institute for Interdisciplinary Sciences Tohoku University Sendai980-8578 Japan Graduate School of Science Osaka University Osaka Toyonaka560-0043 Japan Research Center for Nuclear Physics Osaka University Osaka Ibaraki567-0047 Japan Graduate School of Advanced Technology and Science Tokushima University Tokushima770-8506 Japan Department of Physics Tohoku University Sendai980-8578 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 Physics Departments Duke University North Carolina Central University The University of North Carolina Chapel Hill United States Center for Neutrino Physics Virginia Polytechnic Institute State University BlacksburgVA24061 United States Center for Experimental Nuclear Physics and Astrophysics University of Washington SeattleWA98195 United States Nikhef The University of Amsterdam Science Park Amsterdam1098XG Netherlands Boston University Department of Physics 590 Commonwealth Avenue BostonMA02215 United States

Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter (χ0) accompanied by a negatively charged excited state (χ−) with a small mass difference (e.g. χ0 = 1 TeV and mass difference ∆m = 17 MeV, we set the most stringent upper limits on the recombination cross section times velocity 〈σv〉 and the decay-width of χ− to 9.2 × 10−30 cm3/s and 8.7 × 10−14 GeV, respectively at 90% confidence level. © 2023, CC BY.

关键词： Excited states

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Observation of Robust Zero Energy Extended States

arXiv

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arXiv 2022年

作者： Ferdous, Jannatul Yuce, Cem Alù, Andrea Ramezani, Hamidreza Department of Physics and Astronomy University of Texas Rio Grande Valley EdinburgTX78539 United States Department of Physics Eskisehir Technical University Eskisehir Turkey 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

Topological edge states arise at the interface of two topologically-distinct structures and have two distinct features: they are localized and robust against symmetry protecting disorder. On the other hand, conventional transport in one dimension is associated with extended states, which typically do not have topological robustness. In this paper, using lossy coupled resonators in one dimension, we demonstrate both theoretically and experimentally the existence of robust states residing in the bulk. We show that they are unusually robust against disorders in coupling between adjacent sites and losses. Our work paves the way to a new form of robust transport that is not limited to boundary phenomena and can be accessed more easily from far field. © 2022, CC BY.

关键词： Topology

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Spin Seebeck effect at low temperatures in the nominally paramagnetic insulating state of vanadium dioxide

arXiv

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arXiv 2022年

作者： Luo, Renjie Zhao, Xuanhan Chen, Liyang Legvold, Tanner J. Navarro, Henry Schuller, Ivan K. Natelson, Douglas Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Rice University HoustonTX77005 United States Department of Physics Center for Advanced Nanoscience University of California-San Diego La Jolla CA92093 United States Department of Electrical and Computer Engineering Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

The low temperature monoclinic, insulating phase of vanadium dioxide is ordinarily considered nonmagnetic, with dimerized vanadium atoms forming spin singlets, though paramagnetic response is seen at low temperatures. We find a nonlocal spin Seebeck signal in VO2 films that appears below 30 K and which increases with decreasing temperature. The spin Seebeck response has a non-hysteretic dependence on in-plane external magnetic field. This paramagnetic spin Seebeck response is discussed in terms of prior findings on paramagnetic spin Seebeck effects and expected magnetic excitations of the monoclinic ground state. Copyright © 2022, The Authors. All rights reserved.

关键词： Vanadium dioxide

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In-situ measurements of twist and bend elastic constants in oblique helicoidal cholesteric

arXiv

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arXiv 2022年

作者： Iadlovska, Olena S. Thapa, Kamal Rajabi, Mojtaba Shiyanovskii, Sergij V. Lavrentovich, Oleg D. Advanced Materials and Liquid Crystal Institute Kent State University KentOH44242 United States Department of Physics Kent State University KentOH44242 United States Materials Science Graduate Program Kent State University KentOH44242 United States

Unique electro-optical properties of the oblique helicoidal cholesteric (ChOH) stem from its heliconical director structure. An applied electric field preserves the single harmonic modulation of the director while tuning the ChOH period and the corresponding Bragg peak wavelength within a broad spectral range. We use the response of ChOH to the electric field to measure the elastic constants of twist K22 and bend K33 directly in the cholesteric phase. The temperature dependencies of K22 and K33 allow us to determine the range of the electric tunability of the ChOH pitch and the heliconical angle. The data are important for understanding how molecular composition and chirality influence macroscopic elastic properties of the chiral liquid crystals and for the development of ChOH-based optical devices. © 2022, CC BY.

关键词： Electric fields

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Chiral exceptional point enhanced active tuning and nonreciprocity in micro-resonators

arXiv

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arXiv 2024年

作者： Lee, Hwaseob Chang, Lorry Kecebas, Ali Mao, Dun Xiao, Yahui Li, Tiantian Alù, Andrea Özdemir, Sahin K. Gu, Tingyi Department of Electrical and Computer Engineering University of Delaware NewarkDE19716 United States Department of Engineering Science and Mechanics Pennsylvania State University University ParkPA16802 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 and Computer Engineering Saint Louis University Saint LouisMO63103 United States

Exceptional points (EPs) have been extensively explored in mechanical, acoustic, plasmonic, and photonic systems. However, little is known about the role of EPs in tailoring the dynamic tunability of optical devices. A specific type of EPs known as chiral EPs has recently attracted much attention for controlling the flow of light and for building sensors with better responsivity. A recently demonstrated route to chiral EPs via lithographically defined symmetric Mie scatterers on the rim of resonators has not only provided the much-needed mechanical stability for studying chiral EPs, but also helped reduce losses originating from nanofabrication imperfections, facilitating the insitu study of chiral EPs and their contribution to the dynamics and tunability of resonators. Here, we use asymmetric Mie scatterers to break the rotational symmetry of a microresonator, to demonstrate deterministic thermal tuning across a chiral EP, and to demonstrate EP-mediated chiral optical nonlinear response and efficient electro-optic tuning. Our results indicate asymmetric electro-optic modulation with up to 17dB contrast at GHz and CMOS-compatible voltage levels. Such wafer-scale nano-manufacturing of chiral electro-optic modulators and the chiral EP-tailored tunning may facilitate new micro-resonator functionalities in quantum information processing, electromagnetic wave control, and optical interconnects. © 2024, CC BY.

关键词： Microresonators

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Active Massive Black Hole Found in the Young Star-Forming Dwarf Galaxy SBS 0335-052E

arXiv

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arXiv 2023年

作者： Hatano, Shun Ouchi, Masami Nakajima, Kimihiko Kawaguchi, Toshihiro Kokubo, Mitsuru Kikuta, Satoshi Tominaga, Nozomu Xu, Yi Watanabe, Kuria Harikane, Yuichi Isobe, Yuki Matsumoto, Akinori Nishigaki, Moka Ono, Yoshiaki Onodera, Masato Sugahara, Yuma Umeda, Hiroya 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 University of Tokyo Chiba Kashiwa277-8583 Japan Department of Economics Management and Information Science Onomichi City University Hisayamada 1600-2 Hiroshima Onomichi722-8506 Japan Astronomical Science Program Graduate Institute for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Department of Physics Faculty of Science and Engineering Konan University 8-9-1 Okamoto Hyogo Kobe658-8501 Japan Department of Astronomy Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan Department of Physics Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo Tokyo113-0033 Japan 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

Since the late 20th century, young star-forming dwarf galaxies with extremely low heavy-element abundances have been identified in the local universe1–3. Such a population of galaxies, represented by SBS 0335-052E, is intensively studied as a laboratory of galaxy formation, and interpreted as galaxies with hard emission and energetic outflows driven by massive stars2, 4, 5. Here we report the temporal flux variability of SBS 0335-052E in 3 − 4 µm bands on timescale of months to years with dimming and brightening up to 50% over 12 years. This is a clear signature of dust torus emission of an active massive black hole in SBS 0335-052E. The deep optical spectrum reveals a very broad component with 1.24 (±0.01) × 104 km s−1 in Hα emission, suggesting emission originated from broad line regions around the massive black hole. The black hole mass is estimated to be ∼ 100 thousand solar masses from the spectral energy distribution. This is the first example of the massive black hole existence in a long-considered young star-forming dwarf galaxy. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

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Photoemission of the Upconverted Hot Electrons in Mn-doped CsPbBr3 Nanocrystals

arXiv

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arXiv 2022年

作者： Wang, Chih-Wei Liu, Xiaohan Qiao, Tian Khurana, Mohit Akimov, Alexey V. Son, Dong Hee Department of Chemistry Texas A&M University College StationTX77843 United States Department of Physics Texas A&M University College StationTX77843 United States Center for Nanomedicine Institute for Basic Science Graduate Program of Nano Biomedical Engineering Advanced Science Institute Yonsei University Seoul03722 Korea Republic of

Hot electrons play a crucial role in enhancing the efficiency of photon-to-current conversion or photocatalytic reactions. In semiconductor nanocrystals, energetic hot electrons capable of photoemission can be generated via the upconversion process involving the dopant-originated intermediate state, currently known only in Mn-doped cadmium chalcogenide quantum dots. Here, we report that Mn-doped CsPbBr3 nanocrystals are an excellent platform for generating hot electrons via upconversion that can benefit from various desirable exciton properties and the structural diversity of metal halide perovskites (MHP). 2-dimensional Mn-doped CsPbBr3 nanoplatelets are particularly advantageous for hot electron upconversion due to the strong exciton-dopant interaction mediating the upconversion process. Furthermore, nanoplatelets reveal evidence for the hot electron upconversion via long-lived dark exciton in addition to bright exciton that may enhance the upconversion efficiency. This study not only establishes the feasibility of hot electron upconversion in MHP host but also demonstrates the potential merits of 2-dimensional MHP nanocrystals in hot electron upconversion. © 2022, CC BY.

关键词： Hot electrons

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Spiral Magnetic Field and Their Role on Accretion Dynamics in the Circumnuclear Disk of Sagittarius A*: Insight from λ = 850 µm Polarization Imaging

arXiv

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arXiv 2024年

作者： Sato, Kazuki Shinnaga, Hiroko Furuya, Ray S. Suzuki, Takeru K. Kakiuchi, Kensuke Ott, Jürgen Physics and Astronomy Program Graduate School of Science and Technology Kagoshima University 1-21-35 Korimoto Kagoshima Kagoshima890-0065 Japan Graduate School of Science and Technology Kagoshima University 1-21-35 Korimoto Kagoshima Kagoshima890-0065 Japan Institute of Liberal Arts and Sciences Tokushima University Minami Jousanajima-machi 1-1 Tokushima Tokushima770-8502 Japan National Astronomical Observatory of Japan Tokyo Mitaka Japan School of Arts and Sciences University of Tokyo 3-8-1 Komaba Tokyo Meguro153-8902 Japan National Radio Astronomy Observatory 1003 Lopezville Road SocorroNM87801 United States

We showcase a study on the physical properties of the Circumnuclear Disk (CND) surrounding the SMBH Sgr A* of the Galactic Center, emphasizing the role of magnetic field (B field) with 0.47 pc spatial resolution, based on the sensitive λ = 850 µm polarization data taken with the JCMT SCUBA2/POL2. We analyzed ancillary datasets: CS J = 2 − 1 emission taken with the ALMA, continuum emissions taken at λ = 6 cm and at λ = 37 µm taken with the VLA and SOFIA. The B field within the CND exhibits a coherent spiral pattern. Applying the model described by Wardle and Königl 1990 (WK model) to the observed B field pattern, it favors gas-pressure-dominant models without dismissing a gas-and-B field comparable model, leading us to estimate the B -field strength in the ionized cavity around Sgr A* as (Formula Presented) mG. Analysis based on the WK model further allows us to derive representative B -field strengths for the radial, azimuthal, and vertical components as (Br, B, Bz) = (0.4 ± 0.1, −0.7 ± 0.2, 0.2 ± 0.05) mG, respectively. A key finding is that the |B| component is dominant over Br and Bz components, consistent with the spiral morphology, indicating that the CND’s B -field is predominantly toroidal, possibly shaped by accretion dynamics. Considering the turbulent pressure, estimated plasma β values indicate the effective gas pressure should surpass the magnetic pressure. Assessing the CND of our MWG in the toroidal-and-vertical stability parameter space, we propose that such an "effective" magnetoro-tational instability (MRI) may likely be active. The estimated maximum unstable wavelength, λmax = 0.1 ± 0.1 pc, is smaller than the CND’s scale height (0.2±0.1 pc), which indicates the potential for the effective MRI intermittent cycles of ∼ 106 years, which should profoundly affect the CND’s evolution, considering the estimated mass accretion rate of 10−2M☉ yr−1 to the SMBH. © 2024, CC BY.

关键词： Magnetic fields

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On the Use of Surfactant for Precursor Solution Processing and Influence on the Properties of Tin Dioxide Thin Films

Research Square

引用

Research Square 2021年

作者： Fonseca, Lucas P. Pedrini, Luiz F.K. Lima, João V.M. Escaliante, Lucas C. Santos, Stevan B.O. Scalvi, Luis V.A. School of Sciences Department of Physics Bauru SP 17033-360 Brazil School of Sciences POSMAT - Post-Graduate Program in Materials Science and Technology Bauru SP 17033-360 Brazil

Tin dioxide (SnO2) thin films have several sorts of applications, including as gas sensors and in photocatalysis, where the surface area plays a relevant role. The use of the Triton X-100 non-ionic surfactant in the precursor solution processing has revealed as a fundamental aid to increase adhesion of the SnO2 film on the substrate. Moreover, the surfactant presence leads to a significant increase in the surface area of deposited thin films, and the roughness (rms) increases from 57.6 nm to 275 nm. The influence can also be observed in the XRD profiles, with a higher degree of crystallinity for Triton deposited films. It also increases the defect density and the electron scattering, leading to rather resistive films which are thermally excited only above room temperature. The activation energy for the defect ionization is rather high, 800 meV, but the thermal excitation takes place at a lower temperature range, compared to films prepared without Triton in the solution processing. The performance on photocatalysis is improved for films prepared with Triton X-100, since most of the methylene blue dye is degraded in the first 90 minutes when interacting with the sample. © 2021, CC BY.

关键词： Sol-gels

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Observation of higher-order exceptional points in a non-local acoustic metagrating

arXiv

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arXiv 2021年

作者： Fang, Xinsheng Gerard, Nikhil J.R.K. Zhou, Zhiling Ding, Hua Wang, Nengyin Jia, Bin Deng, Yuanchen Wang, Xu Jing, Yun Li, Yong Institute of Acoustics School of Physics Science and Engineering Tongji University Shanghai200092 China Graduate Program in Acoustics Penn State University University ParkPA16802 United States

Higher-order exceptional points have attracted increased attention in recent years due to their enhanced sensitivity and distinct topological features. Here, we show that nonlocal acoustic metagratings that enable precise and simultaneous control over their muliple orders of diffraction, can serve as a robust platform for investigating higher-order exceptional points in free space. The proposed metagratings, not only could advance the fundamental research of arbitrary order exceptional points, but could also empower unconventional free-space wave manipulation for applications related to sensing and extremely asymmetrical wave control. © 2021, CC BY.

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