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arXiv 2024年

作者： Zhong, Yu-Jie Li, Jia-Cheng Huang, Xuan-Fu Lee, Ying-Je Chen, Ting-Zhen Zhang, Jia-Ren Huang, Angus Hsu, Hsiu-Chuan Ortix, Carmine Chang, Ching-Hao Department of Physics National Cheng Kung University Tainan70101 Taiwan National Cheng Kung University Tainan70101 Taiwan Program on Key Materials Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan70101 Taiwan Department of Physics National Tsing Hua University Hsinchu30013 Taiwan Graduate Institute of Applied Physics National Chengchi University Taipei11605 Taiwan Dipartimento di Fisica E. R. Caianiello Università di Salerno Fisciano SalernoI-84084 Italy

We theoretically demonstrate that carbon nanoscrolls – spirally wrapped graphene layers with open endpoints – can be characterized by a large positive magnetoconductance. We show that when a carbon nanoscroll is subject to an axial magnetic field of several Tesla, the ballistic conductance at low carrier densities of the nanoscroll has an increase of about 200%. Importantly, we find that this positive magnetoconductance is not only preserved in an imperfect nanoscroll (with disorder or mild inter-turn misalignment) but can even be enhanced in the presence of on-site disorder. We prove that the positive magnetoconductance comes about the emergence of magnetic field-induced zero energy modes, specific of rolled-up geometries. Our results establish curved graphene systems as a new material platform displaying sizable magnetoresistive phenomena. © 2024, CC BY.

关键词： Magnetic fields

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Low-energy astrophysics with KamLAND 37

Low-energy astrophysics with KamLAND

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37th International Cosmic Ray Conference, ICRC 2021

作者： Kawada, Nanami Obara, Shuhei Ishidoshiro, Koji Grant, C. O’Donnell, T. Dell’Oro, S. Abe, S. Asami, S. Gando, A. Gando, Y. Gima, T. Goto, A. Hachiya, T. Hata, K. Hayashida, S. Hosokawa, K. Ichimura, K. Ieki, S. Ikeda, H. Inoue, K. Kamei, Y. 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. Ueshima, K. Wada, Y. Watanabe, H. Yoshida, Y. Ichikawa, A.K. Kozlov, A. Chernyak, D. Takemoto, Y. Yoshida, S. Umehara, S. Fushimi, K. Nakamura, K.Z. Yoshida, M. Berger, B.E. Fujikawa, B.K. Learned, J.G. Maricic, J. Axani, S.N. 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. Research Center for Neutrino Science Tohoku University Sendai980-8578 Japan Frontier Research Institute for Interdisciplinary Sciences 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 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 Department of Physics Kyoto University Kyoto606-8502 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 Physics Department 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 two results of a search for MeV-scale neutrino and anti-neutrino events correlated with gravitational wave events/candidates and large solar flares with KamLAND. The KamLAND detector is a large-volume neutrino detector using liquid scintillator, which is located at 1 km underground under the top of Mt. Ikenoyama in Kamioka, Japan. KamLAND has multiple reaction channels to detect neutrinos. Electron antineutrino can be detected via inverse-beta decay with 1.8 MeV neutrino energy threshold. All flavors of neutrinos can be detected via neutrino-electron scattering without neutrino energy threshold. KamLAND has continued the neutrino observation since 2002 March. We use the data set of 60 gravitational waves provided by the LIGO/Virgo collaboration during their second and third observing runs and search for coincident electron antineutrino events in KamLAND. We find no significant coincident signals within a ±500 s timing window from each gravitational wave and present 90% C.L. upper limits on the electron antineutrino fluence between 108–1013 cm−2 for neutrino energies of 1.8–111 MeV. For a solar-flare neutrino search at KamLAND, we determine the timing window using the solar X-ray data set provided by the GOES satellite series from 2002 to 2019 and search for the excess of coincident event rate on the all-flavor neutrinos. We find no significant event rate excess in the flare time windows and get 90% C.L. upper limits on the fluence of neutrinos of all flavors (electron anti-neutrinos) between 1010–1013 cm−2 (108–1013 cm−2) for neutrino energies in the energy range of 0.4–35 MeV. © Copyright owned by the author(s).

关键词： Gravity waves

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Counting edge modes via dynamics of boundary spin impurities

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Physical Review B 2023年第14期108卷 L140301-L140301页

作者： Umar Javed Jamir Marino Vadim Oganesyan Michael Kolodrubetz Department of Physics The University of Texas at Dallas Richardson Texas 75080 USA Institut für Physik Johannes Gutenberg-Universität Mainz D-55099 Mainz Germany Physics Program and Initiative for the Theoretical Sciences The Graduate Center CUNY New York New York 10016 USA Department of Physics and Astronomy College of Staten Island CUNY Staten Island New York 10314 USA Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New York New York 10010 USA

We study the dynamics of the one-dimensional Ising model in the presence of a static symmetry-breaking boundary field via the two-time autocorrelation function of the boundary spin. We find oscillatory correlations that decay as power laws. We uncover a phase diagram of dynamical responses where, upon tuning the strength of the boundary field, we observe distinct power laws that directly correspond to changes in the number of edge modes as the boundary and bulk magnetic field are varied. We suggest how the universal physics can be demonstrated in current experimental setups, such as Rydberg chains.

关键词： Edge states Quantum phase transitions Ising model Single impurity model

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Magneto-optical Spectroscopy with RAMBO: A Table-Top 30 T Magnet

arXiv

引用

arXiv 2022年

作者： Tay, Fuyang Baydin, Andrey Katsutani, Fumiya Kono, Junichiro Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Optically probing materials in high magnetic fields can provide enlightening insight into field-modified electronic states and phases, while optically driving materials in high magnetic fields can induce novel nonequilibrium many-body dynamics of spin and charge carriers. While there are high-field magnets compatible with standard optical spectroscopy methods, they are generally bulky and have limited optical access, which prohibit performing state-of-the-art ultrafast and/or nonlinear optical experiments. The Rice Advanced Magnet with Broadband Optics (RAMBO), a unique 30-T pulsed mini-coil magnet system with direct optical access, has enabled previously challenging experiments using femtosecond optical pulses, including time-domain terahertz spectroscopy, in cutting-edge materials placed in strong magnetic fields. Here, we review recent experimental advances made possible by the first-generation RAMBO setup. After summarizing technological aspects of combining optical spectroscopic techniques with the mini-coil magnet, we describe results of magneto-optical studies of a wide variety of materials, providing new insight into the states and dynamics of four types of quasiparticles in solids – excitons, plasmons, magnons, and phonons – in high magnetic fields. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnets

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Cubic ferromagnet and emergent U(1) symmetry on its phase boundary

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Physical Review B 2023年第22期107卷 224406-224406页

作者： Wei-Lin Tu Xinliang Lyu S. R. Ghazanfari Huan-Kuang Wu Hyun-Yong Lee Naoki Kawashima Division of Display and Semiconductor Physics Korea University Sejong 30019 Korea Faculty of Science and Technology Keio University 3-14-1 Hiyoshi Kohoku-ku Yokohama 223-8522 Japan Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277-8581 Japan Department of Physics Condensed Matter Theory Center and Joint Quantum Institute University of Maryland College Park Maryland 20742 USA Department of Applied Physics Graduate School Korea University Sejong 30019 Korea Interdisciplinary Program in E.ICT-Culture-Sports Convergence Korea University Sejong 30019 Korea Trans-scale Quantum Science Institute The University of Tokyo Bunkyo Tokyo 113-0033 Japan

We study the simplest quantum lattice spin model for the two-dimensional (2D) cubic ferromagnet by means of mean-field analysis and tensor network calculation. While both methods give rise to similar results in detecting related phases, the 2D infinite projected entangled-pair state (iPEPS) calculation provides more accurate values of transition points. Near the phase boundary, moreover, our iPEPS results indicate that it is more difficult to pin down the orientation of magnetic easy axes, and we interpret it as the easy-axis softening. This phenomenon implies an emergence of continuous U(1) symmetry, which is indicated by the low-energy effective model and has been analytically shown by the field theory. Our model and study provide a concrete example for utilizing iPEPS near the critical region, showing that the emergent phenomenon living on the critical points can already be captured by iPEPS with a rather small bond dimension.

关键词： Magnetic anisotropy Magnetism Quantum criticality Projected entangled pair states Tensor network methods

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Ferroelectric transistors based on shear-transformation-mediated rhombohedral-stacked molybdenum disulfide

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Nature Electronics 2024年第1期7卷 29-38页

作者： Yang, Tilo H. Liang, Bor-Wei Hu, Hsiang-Chi Chen, Fu-Xiang Ho, Sheng-Zhu Chang, Wen-Hao Yang, Liu Lo, Han-Chieh Kuo, Tzu-Hao Chen, Jyun-Hong Lin, Po-Yen Simbulan, Kristan Bryan Luo, Zhao-Feng Chang, Alice Chinghsuan Kuo, Yi-Hao Ku, Yu-Seng Chen, Yi-Cheng Huang, You-Jia Chang, Yu-Chen Chiang, Yu-Fan Lu, Ting-Hua Lee, Min-Hung Li, Kai-Shin Wu, Menghao Chen, Yi-Chun Lin, Chun-Liang Lan, Yann-Wen Department of Physics National Taiwan Normal University Taipei Taiwan Taiwan Semiconductor Research Institute National Applied Research Laboratories Hsinchu Taiwan Department of Electrophysics National Yang Ming Chiao Tung University Hsinchu Taiwan Department of Physics National Cheng Kung University Tainan Taiwan School of Physics Huazhong University of Science and Technology Wuhan China Institute of Cellular and Organismic Biology Academia Sinica Taipei Taiwan Department of Mathematics and Physics University of Santo Tomas Manila Philippines Program for Semiconductor Devices Materials and Hetero-integration Graduate School of Advanced Technology National Taiwan University Taipei Taiwan Hsinchu Taiwan Department of Physics National Taiwan University Taipei Taiwan Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA United States

To develop low-power, non-volatile computing-in-memory device using ferroelectric transistor technologies, ferroelectric channel materials with scaled thicknesses are required. Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), equipped with sliding ferroelectricity could provide an answer. However, achieving switchable electric polarization in epitaxial MoS2 remains challenging due to the absence of mobile domain boundaries. Here we show that polarity-switchable epitaxial rhombohedral-stacked (3R) MoS2 can be used as a ferroelectric channel in ferroelectric memory transistors. We show that a shear transformation can spontaneously occur in 3R MoS2 epilayers, producing heterostructures with stable ferroelectric domains embedded in a highly dislocated and unstable non-ferroelectric matrix. This diffusionless phase transformation process produces mobile screw dislocations that enable collective polarity control of 3R MoS2 via an electric field. Polarization–electric-field measurements reveal a switching field of 0.036 V nm−1 for shear-transformed 3R MoS2. Our sliding ferroelectric transistors are non-volatile memory units with thicknesses of only two atomic layers and exhibit an average memory window of 7 V with an applied voltage of 10 V, retention times greater than 104 seconds and endurance greater than 104 cycles. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.

关键词： Molybdenum disulfide

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The connection between polymer collapse and the onset of jamming

arXiv

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arXiv 2023年

作者： Grigas, Alex T. Fisher, Aliza Shattuck, Mark D. O’Hern, Corey S. Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States Integrated Graduate Program in Physical and Engineering Biology Yale University New HavenCT06520 United States Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department The City College of New York New YorkNY10031 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

Previous studies have shown that the interiors of proteins are densely packed, reaching packing fractions that are as large as those found for static packings of individual amino-acid-shaped particles. How can the interiors of proteins take on such high packing fractions given that amino acids are connected by peptide bonds and many amino acids are hydrophobic with attractive interactions? We investigate this question by comparing the structural and mechanical properties of collapsed attractive disk-shaped bead-spring polymers to those of three reference systems: static packings of repulsive disks, of attractive disks, and of repulsive disk-shaped bead-spring polymers. We show that attractive systems quenched to temperatures below the glass transition T Tg and static packings of both repulsive disks and bead-spring polymers possess similar interior packing fractions. Previous studies have shown that static packings of repulsive disks are isostatic at jamming onset, i.e. the number of contacts Nc matches the number of degrees of freedom, which strongly influences their mechanical properties. We find that repulsive polymers are hypostatic at jamming onset, but effectively isostatic when including quartic modes. While attractive disk and polymer packings are hyperstatic, we identify a definition for interparticle contacts for which they can also be considered as effectively isostatic. As a result, we show that the mechanical properties (e.g. scaling of the potential energy with excess contact number and low-frequency contribution to the density of vibrational modes) of weakly attractive disk and polymer packings are similar to those of isostatic repulsive disk and polymer packings. Our results demonstrate that static packings generated via attractive collapse or compression of repulsive particles possess similar structural and mechanical properties. © 2023, CC BY.

关键词： Amino acids

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Two-Step Machine Learning Approach for Charge-Transfer Coupling with Structurally Diverse Data

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Journal of Physical Chemistry A 2024年第1期128卷 271-280页

作者： Lin, Hung-Hsuan Wang, Chun-I Yang, Chou-Hsun Secario, Muhammad Khari Hsu, Chao-Ping Institute of Chemistry Academia Sinica 128 Section 2 Academia Road Nankang Taipei115 Taiwan Taiwan International Graduate Program on Sustainable Chemical Science & Technology Academia Sinica Institute of Chemistry 128 Academia Road Sec.2 Nankang Taipei115 Taiwan Department of Applied Chemistry National Yang Ming Chiao Tung University 1001 University Road Hsinchu300 Taiwan Division of Physics National Center for Theoretical Sciences 1 Section 4 Roosevelt Road Taipei106 Taiwan Molecular Science and Digital Innovation Center Genetics Generation Advancement Corp No. 28 Ln. 36 Xinhu First Rd. Neihu Taipei114 Taiwan Department of Chemistry University of Illinois at Urbana-Champaign UrbanaIL61801 United States

Electronic coupling is important in determining charge-transfer rates and dynamics. Coupling strength is sensitive to both intermolecular, e.g., orientation or distance, and intramolecular degrees of freedom. Hence, it is challenging to build an accurate machine learning model to predict electronic coupling of molecular pairs, especially for those derived from the amorphous phase, for which intermolecular configurations are much more diverse than those derived from crystals. In this work, we devise a new prediction algorithm that employs two consecutive KRR models. The first model predicts molecular orbitals (MOs) from structural variation for each fragment, and coupling is further predicted by using the overlap integral included in a second model. With our two-step procedure, we achieved mean absolute errors of 0.27 meV for an ethylene dimer and 1.99 meV for a naphthalene pair, much improved accuracy amounting to 14-fold and 3-fold error reductions, respectively. In addition, MOs from the first model can also be the starting point to obtain other quantum chemical properties from atomistic structures. This approach is also compatible with a MO predictor with sufficient accuracy. © 2023 American Chemical Society.

关键词： Molecular orbitals

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Analysis of high-power packages for white-light-emitting diode lamps with remote phosphor

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MRS Online Proceedings Library 2021年第1期892卷 166-171页

作者： Hong Luo Jong Kyu Kim Yangang Xi E. Fred Schubert Jaehee Cho Cheolsoo Sone Yongjo Park Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy USA Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy USA Photonics Program Team Samsung Advanced Institute of Technology Suwon Korea

An optimized packaging configuration for high-power white-light-emitting diode (LED) lamps that employs a diffuse reflector cup, a remote phosphor and a hemi-spherically-shaped encapsulation is presented. Ray tracing simulations for this configuration show that the phosphor efficiency can be enhanced by up to 50% over conventional packages. It is experimentally shown that dichromatic LED lamps with remote phosphor and diffuse reflector cup configuration have higher phosphor efficiency by 15.4% for blue-pumped yellow phosphor and by 27% for ultraviolet-pumped blue phosphor over conventional packages. Those improvements are attributed to reduced absorption of the phosphorescence by the LED chip and the reduction of deterministic optical modes trapped inside the encapsulant.

关键词： packaging optoelectronic optical properties

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Model selection using time-delay lenses

arXiv

引用

arXiv 2022年

作者： Melia, Fulvio Wei, Jun-Jie Wu, Xue-Feng Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China

The sample of time-delay gravitational lenses appropriate for studying the geometry of the Universe continues to grow as dedicated campaigns, such as the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope, complete their census of high-redshift sources. This catalog now includes hundreds of strong lensing systems, at least 31 of which have reasonably accurate time delay measurements. In this paper, we use them to compare the predictions of two competing Friedmann-Lemaître-Robertson-Walker models: flat ΛCDM, characterized by two adjustable parameters (H0 and Ωm), and the Rh = ct universe (with H0 as the single free variable). Over the past decade, the latter has accounted for the data better than the standard model, most recently the emergence of well-formed galaxies discovered by JWST at cosmic dawn. Here we show that the current sample of time-delay lenses favours Rh = ct with a likelihood of ∼ 84% versus ∼ 16% for the standard model. This level of accuracy will greatly improve as the ongoing surveys uncover many thousands additional lens systems over the next several years. © 2022, CC BY.

关键词： Time delay

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