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arXiv 2024年

作者： Waters, Dacen Okounkova, Anna Su, Ruiheng Zhou, Boran Yao, Jiang Watanabe, Kenji Taniguchi, Takashi Xu, Xiaodong Zhang, Ya-Hui Folk, Joshua Yankowitz, Matthew Department of Physics University of Washington SeattleWA98195 United States Intelligence Community Postdoctoral Research Fellowship Program University of Washington SeattleWA98195 United States Quantum Matter Institute University of British Columbia VancouverBCV6T 1Z1 Canada Department of Physics and Astronomy University of British Columbia VancouverBCV6T 1Z1 Canada Department of Physics and Astronomy Johns Hopkins University BaltimoreMD21205 United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Materials Science and Engineering University of Washington SeattleWA98195 United States

The rapid development of moiré quantum matter has recently led to the remarkable discovery of the fractional quantum anomalous Hall effect [1–6], and sparked predictions of other novel correlation-driven topological states [7–29]. Here, we investigate the interplay of electronic crystals with integer and fractional Chern insulators in a moiré lattice of rhomobohedral pentalayer graphene (RPG) aligned with hexagonal boron nitride. At a doping of one electron per moiré unit cell, we see a correlated insulator with a Chern number that can be tuned between C = 0 and +1 by an electric displacement field, accompanied by an array of other such insulators formed at fractional band fillings, ν. Collectively, these states likely correspond to trivial and topological electronic crystals, some of which spontaneously break the discrete translational symmetry of the moiré lattice. Upon applying a modest magnetic field, a narrow region forms around ν = 2/3 in which transport measurements imply the emergence of a fractional Chern insulator, along with hints of weaker states at other fractional ν. In the same sample, we also see a unique sequence of incipient Chern insulators arising over a broad range of incommensurate band filling near two holes per moiré unit cell. Our results establish moiré RPG as a fertile platform for studying the competition and potential intertwining of electronic crystallization and topological charge fractionalization. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum Hall effect

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Observation of the dual quantum spin Hall insulator by density-tuned correlations in a van der Waals monolayer

arXiv

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arXiv 2024年

作者： Tang, Jian Ding, Thomas Siyuan Chen, Hongyu Gao, Anyuan Qian, Tiema Huang, Zumeng Sun, Zhe Han, Xin Strasser, Alex Li, Jiangxu Geiwitz, Michael Shehabeldin, Mohamed Belosevich, Vsevolod Wang, Zihan Wang, Yiping Watanabe, Kenji Taniguchi, Takashi Bell, David C. Wang, Ziqiang Fu, Liang Zhang, Yang Qian, Xiaofeng Burch, Kenneth S. Shi, Youguo Ni, Ni Chang, Guoqing Xu, Su-Yang Ma, Qiong Department of Physics Boston College Chestnut HillMA United States Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore Singapore Department of Chemistry and Chemical Biology Harvard University CambridgeMA United States Department of Physics and Astronomy and California NanoSystems Institute University of California Los Angeles Los AngelesCA United States Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China Department of Materials Science and Engineering Texas A&M University College StationTX United States Department of Physics and Astronomy University of Tennessee KnoxvilleTN United States Min H. Kao Department of Electrical Engineering and Computer Science University of Tennessee KnoxvilleTN United States Research Center for Electronic and Optical Materials National Institute for Materials Science Tsukuba Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science Tsukuba Japan Harvard John A. Paulson School of Engineering and Applied Sciences The Center for Nanoscale system Harvard University CambridgeMA United States Department of Physics Massachusetts Institute of Technology CambridgeMA United States CIFAR Azrieli Global Scholars program CIFAR Toronto Canada

The convergence of topology and correlations represents a highly coveted realm in the pursuit of novel quantum states of matter [1, 2]. Introducing electron correlations to a quantum spin Hall (QSH) insulator can lead to the emergence of a fractional topological insulator and other exotic time-reversal-symmetric topological order [3- 10], not possible in quantum Hall and Chern insulator systems. However, the QSH insulator with quantized edge conductance remains rare, let alone that with significant correlations. In this work, we report a novel dual QSH insulator within the intrinsic monolayer crystal of TaIrTe4, arising from the interplay of its single-particle topology and density-tuned electron correlations. At charge neutrality, monolayer TaIrTe4 demonstrates the QSH insulator that aligns with single-particle band structure calculations, manifesting enhanced nonlocal transport and quantized helical edge conductance. Interestingly, upon introducing electrons from charge neutrality, TaIrTe4 only shows metallic behavior in a small range of charge densities but quickly goes into a new insulating state, entirely unexpected based on TaIrTe4's single-particle band structure. This insulating state could arise from a strong electronic instability near the van Hove singularities (VHS), likely leading to a charge density wave (CDW). Remarkably, within this correlated insulating gap, we observe a resurgence of the QSH state, marked by the revival of nonlocal transport and quantized helical edge conduction. Our observation of helical edge conduction in a CDW gap could bridge spin physics and charge orders. The discovery of a dual QSH insulator introduces a new method for creating topological flat minibands via CDW superlattices, which offer a promising platform for exploring time-reversal-symmetric fractional phases and electromagnetism [3-5, 11, 12]. Copyright © 2024, The Authors. All rights reserved.

关键词： Charge density waves

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Mechanism of THz dielectric constant enhancement in multi-component oxide glasses investigated by infrared and THz spectroscopies

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Journal of Physics and Chemistry of Solids 2023年 176卷

作者： Wada, Osamu Ramachari, Doddoji Yang, Chan-Shan Harada, Yukihiro Uchino, Takashi Pan, Ci-Ling Department of Physics National Tsing Hua University Hsinchu30013 Taiwan Office for Academic and Industrial Innovation Kobe University Kobe657-8501 Japan Institute of Research and Development Duy Tan University Da Nang550000 Viet Nam Faculty of Natural Sciences Duy Tan University Da Nang550000 Viet Nam Institute and Undergraduate Program of Electro-Optical Engineering National Taiwan Normal University Taipei11677 Taiwan Micro/Nano Device Inspection and Research Center National Taiwan Normal University Taipei106 Taiwan Graduate School of Engineering Kobe University Kobe657-8501 Japan Graduate School of Science Kobe University Kobe657-8501 Japan

Dielectric properties of multi-component silicate oxide glasses are investigated with a focus on high dielectric constant oxyfluorosilicate (OFS) glasses by using the infrared reflection spectroscopy and terahertz (THz) time-domain spectroscopy. On the basis of multiple Lorentz oscillator model, vibrational parameters and most responsible ionic pairs are identified for major modes in OFS glasses. The lowest frequency mode is found to dominate the total THz dielectric strength. Among various glasses, the high frequency (optical) dielectric constant shows a superlinear dependence on the electronic polarizability of oxygens. In contrast, the low frequency (THz) mode contribution to the dielectric constant is enhanced by the ionicity (expressed by the polarization ionicity parameter) and exhibits an even steeper dependence on the electronic polarizability. This feature well explains the mechanism of attaining the highest THz dielectric constant in an OFS glass (e.g. ZNbKLSNd glass). Also, the oxygen ion effective charges bearing the lowest frequency modes of OFS glasses are evaluated and found to behave consistently with the polarization ionicity parameter, confirming the relevance of both of these parameters as good ionicity indicators. © 2023 Elsevier Ltd

关键词： Glass

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Moiré exciton polaron engineering via twisted hBN

arXiv

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arXiv 2024年

作者： Cho, Minhyun Datta, Biswajit Han, Kwanghee Chand, Saroj B. Adak, Pratap Chandra Yu, Sichao Li, Fengping Watanabe, Kenji Taniguchi, Takashi Hone, James Jung, Jeil Grosso, Gabriele Kim, Young Duck Menon, Vinod M. Department of Physics Kyung Hee University 26 Kyungheedae-ro Seoul02447 Korea Republic of Department of Physics City College of New York New YorkNY10031 United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Department of Physics Department of Smart Cities University of Seoul Seoul02504 Korea Republic of Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Mechanical Engineering Columbia University New YorkNY10027 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States Department of Information Display Kyung Hee University Seoul02447 Korea Republic of

Twisted hexagonal boron nitride (thBN) exhibits emergent ferroelectricity due to the formation of moiré superlattices with alternating AB and BA domains. These domains possess electric dipoles, leading to a periodic electrostatic potential that can be imprinted onto other 2D materials placed in its proximity. Here we demonstrate the remote imprinting of moiré patterns from twisted hexagonal boron nitride (thBN) onto monolayer MoSe2 and investigate the resulting changes in the exciton properties. We confirm the imprinting of moiré patterns on monolayer MoSe2 via proximity using Kelvin probe force microscopy (KPFM) and hyperspectral photoluminescence (PL) mapping. By developing a technique to create large ferroelectric domain sizes ranging from 1 µm to 8.7 µm, we achieve unprecedented potential modulation of ∼ 387±52 meV. We observe the formation of exciton polarons due to charge redistribution caused by the antiferroelectric moiré domains and investigate the optical property changes induced by the moiré pattern in monolayer MoSe2 by varying the moiré pattern size down to ∼110 nm. Our findings highlight the potential of twisted hBN as a platform for controlling the optical and electronic properties of 2D materials for optoelectronic and valleytronic applications. © 2024, CC BY-NC-ND.

关键词： Boron nitride

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From Challenges and Pitfalls to Recommendations and Opportunities: Implementing Federated Learning in Healthcare

arXiv

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arXiv 2024年

作者： Li, Ming Xu, Pengcheng Hu, Junjie Tang, Zeyu Yang, Guang Bioengineering Department Imperial-X Imperial College London LondonW12 7SL United Kingdom National Heart and Lung Institute Imperial College London LondonSW7 2AZ United Kingdom Athinoula A. Martinos Center for Biomedical Imaging Massachusetts General Hospital BostonMA United States State Key Laboratory of Extreme Photonics and Instrumentation College of Optical Science and Engineering Zhejiang University Hangzhou China Tri-Institutional Computational Biology & Medicine Program Weill Cornell Medicine of Cornell University New York United States Cardiovascular Research Centre Royal Brompton Hospital LondonSW3 6NP United Kingdom School of Biomedical Engineering & Imaging Sciences King’s College London LondonWC2R 2LS United Kingdom

Federated learning holds great potential for enabling large-scale healthcare research and collaboration across multiple centres while ensuring data privacy and security are not compromised. Although numerous recent studies suggest or utilize federated learning based methods in healthcare, it remains unclear which ones have potential clinical utility. This review paper considers and analyzes the most recent studies up to May 2024 that describe federated learning based methods in healthcare. After a thorough review, we find that the vast majority are not appropriate for clinical use due to their methodological flaws and/or underlying biases which include but are not limited to privacy concerns, generalization issues, and communication costs. As a result, the effectiveness of federated learning in healthcare is significantly compromised. To overcome these challenges, we provide recommendations and promising opportunities that might be implemented to resolve these problems and improve the quality of model development in federated learning with healthcare. © 2024, CC BY-NC-ND.

关键词： Federated learning

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High efficiency (Eqe>30%) tadf-oled with lightly-doped emitter (0.5%) by using tadf-host 57th

High efficiency (Eqe>30%) tadf-oled with lightly-doped emitt...

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57th SID International Symposium, Seminar and Exhibition, Display Week, 2020

作者： Ding, Wen-Cheng Huang, Jau-Jiun Chen, Chia-Hsun Chiu, Tien-Lung Lin, Chi-Feng Leung, Man-Kit Lee, Jiun-Haw Graduate Institute of Photonics and Optoelectronics Department of Electrical Engineering National Taiwan University Taipei10617 Taiwan Department of Chemistry Institute of Polymer Science and Engineering National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan Department of Electrical Engineering Program C Yuan Ze University No.135 Yuandong Rd. Zhongli Dist. Taoyuan City320 Taiwan Department of Electro-Optical Engineering National United University No.2 Lienda Nanshi Li Miaoli City Miaoli County36063 Taiwan

High efficiency (EQE=30.15%) organic light emitting diode (OLED) was demonstrated by lightly doping the thermally activated delayed fluorescence (TADF) emitter (0.5%) into the TADF host, resulting from: (1) efficient energy transfer from host to dopant, (2) long exciton diffusion length in host, and (3) rare concentration quenching due to lightly-doped condition. © 2020 SID.

关键词： Organic light emitting diodes (OLED)

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Experimental and Theoretical Insights on the optical and Morphological Properties of Germanium Oxide Thin Films Deposited Via RF Magnetron Sputtering

SSRN

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SSRN 2022年

作者： Tüzemen, Ebru Şenadım Hopoğlu, Hicret Sarıtaş, Sevda Aydınoğlu, Hafize Seda Ertuğrul, Mehmet Maslov, Mikhail M. Kaya, Savaş Ungan, Fatih Gür, Emre Nanophotonics Research and Application Center Sivas Cumhuriyet University Sivas58140 Turkey Department of Physics Faculty of Science Sivas Cumhuriyet University Sivas58140 Turkey Faculty of Technology Department of Optical Engineering Sivas Cumhuriyet University Sivas58140 Turkey İspir Hamza Polat Vocatioanal School Ataturk University Erzurum Turkey Department of Medical Services and Techniques Program of Opticianry Vocational School of Healthcare Sivas Cumhuriyet University Sivas58140 Turkey Department of Electrical and Electronics Engineering Faculty of Engineering Atatürk University Erzurum25240 Turkey Department of Condensed Matter Physics National Research Nuclear University "MEPhI" Kashirskoe Shosse 31 Moscow115409 Russia Health Services Vocational School Department of Pharmacy Sivas Cumhuriyet University Sivas58140 Turkey Department of Physics Faculty of Science Ataturk University Erzurum25240 Turkey

In this study, the optical and morphological properties of germanium oxide (GeO2) thin films have been investigated by experimental and theoretical methods. The films were produced by reactive radio frequency magnetron sputtering (RFMS) under varying oxygen partial pressures ratio to the total pressure, 2%, 4%, 6%, 8%. The optical and structural properties of the films grown have been studied experimentally and theoretical calculations have been presented using density functional theory (DFT). As the x-ray diffraction (XRD) analysis is considered, Ge (111) peak has been observed in the films produced at 2% oxygen partial pressure ratio compared to all the other films has determined to be amorphous. Except for 2% film, the other films were annealed at 900oC, and as a result, GeO2 (101), GeO2 (110), GeO2 (102) and GeO2 (111) peaks were observed. The 2% film was annealed at different annealing temperatures (800, 850, 900, 950oC). As a result, the crystal property has changed compared to the others. It was found that the optical properties of the films grown are strongly dependent on the O2 pressures used. Although the 8% film has a fairly sharp absorption edge, the others are bad. The energy band gap increased with increasing oxygen. After annealing at 900oC, the absorption edge of the films showed a sharp behavior except 4%. There are Ge-O-Ge antisymmetric stretching peaks appeared at 861.51 cm-1, 949.94 cm-1 and symmetric stretching of hexagonal peaks at 516.34 cm-1, 546.29 cm-1, 581.95 cm-1. The results of Density Functional Theory calculations are in good agreement with experimental observations. © 2022, The Authors. All rights reserved.

关键词： optical properties

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Unique chemical composition of the very metal-poor star LAMOST J1645+4357

arXiv

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arXiv 2023年

作者： Aoki, Wako Li, Haining Tominaga, Nozomu Matsuno, Tadafumi Honda, Satoshi Zhao, Gang National Astronomical Observatory of Japan National Institutes of Natural Sciences 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Astronomical Science Program Graduate Institute for Advanced Studies SOKENDAI 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Key Lab of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences A20 Datun Road Chaoyang Beijing100012 China Department of Physics Faculty of Science and Engineering Konan University 8-9-1 Okamoto Hyogo Kobe658-8501 Japan Kapteyn Astronomical Institute University of Groningen Landleven 12 Groningen9747 AD Netherlands Nishi-Harima Astronomical Observatory Center for Astronomy University of Hyogo 407-2 Nishigaichi Sayo-cho Hyogo Sayo679-5313 Japan

We report on the chemical composition of the very metal-poor ([Fe/H]= −2.9) star LAMOST J1645+4357 that is identified to be a red giant having peculiar abundance ratios by Li et al. (2022). The standard abundance analysis is carried out for this object and the well studied metal-poor star HD 122563 that has similar atmospheric parameters. LAMOST J1645+4357 has a remarkable abundance set, highlighted by these features: (1) Nitrogen is significantly enhanced ([N/Fe]= +1.4) and the total abundance of C and N is also very high ([(C+N)/Fe]=+0.9);(2) α-elements are over-abundant with respect to iron as generally found in very metal-poor stars;(3) Ti, Sc, Co and Zn are significantly deficient;(4) Cr and Mn are enhanced compared to most of very metal-poor stars;(5) Sr and Ba are deficient and the Sr/Ba ratio ([Sr/Ba]= −1.0) is significantly lower than the value expected for the r-process. The overall abundance pattern of this object from C to Zn is well reproduced by a faint supernova model assuming spherical explosion, except for the excess of Cr and Mn which requires enhancement of incomplete Si burning or small contributions of a type Ia supernova or a pair-instability supernova. There remains, however, a question why the abundance pattern of this star is so unique among very metal-poor stars. Copyright © 2023, The Authors. All rights reserved.

关键词： Supernovae

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A polarization-insensitive fishnet/spacer/mirror plasmonic absorber for hot electron photodetection application

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Chinese Optics Letters 2020年第5期18卷 63-67页

作者： Zhiqiang Yang Kang Du Wending Zhang Soojin Chua Ting Mei Key Laboratory of Space Applied Physics and Chemistry Ministry of Educationand Shaanxi Key Labora tory of Optical Information TechnologySchool of ScienceNorth Western Polytechnical UniversityXi'an 710072China Department of Electrical and Computer Engineering National University of SingaporeSingapore 117583Singapore LEES Program Singapore-MIT Alliance for Research&Technology(SMART)Singapore 138602Singapore

A polarization-insensitive plasmonic absorber is designed consisting of Au fishnet structures on a TiO2 spacer/Ag mirror. The fishnet structures excite localized surface plasmon and generate hot electrons from the absorbed photons, while the TiO2 layer induces Fabry–Perot resonance, and the Ag mirror acts as a back *** optimizing the TiO2 layer thickness, numerical simulation shows that 97% of the incident light is absorbed in the Au layer. The maximum responsivity and external quantum efficiency of the device can approach 5 mA/W and ~1%, respectively, at the wavelength of 700 nm.

关键词： plasmonic absorber Fabry–Perot resonance internal photoemission surface plasmon

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Large-scale expanded sample imaging with tiling lattice lightsheet microscopy

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The international journal of biochemistry & cell biology 2023年 154卷 106340页

作者： Chieh-Han Lu Cheng-Yu Huang Xuejiao Tian Peilin Chen Bi-Chang Chen Research Center for Applied Sciences Academia Sinica Taipei 115 Taiwan Institute and Undergraduate Program of Electro-Optical Engineering National Taiwan Normal University Taipei 116 Taiwan. Electronic address: chenb10@gate.sinica.edu.tw. Research Center for Applied Sciences Academia Sinica Taipei 115 Taiwan. Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 115 Taiwan Department of Engineering and System Science National Tsing Hua University Hsinchu 300 Taiwan. Institute of Physics Academia Sinica Taipei 115 Taiwan.

The ability to observe biological nanostructures forms a vital step in understanding their functions. Thanks to the invention of expansion microscopy (ExM) technology, super-resolution features of biological samples can now be easily visualized with conventional light microscopies. However, when the sample is physically expanded, the demand for deep and precise 3D imaging increases. Lattice lightsheet microscopy (LLSM), which utilizes a planar illumination that is confined within the imaging depth of high numerical aperture (NA=1.1) detection objective, fulfils such requirements. In addition, optical tiling could be implemented to increase the field of view (FoV) by moving the lightsheet without mechanically moving the samples or the objective for high-precision 3D imaging. In this review article, we will explain the principle of the tiling lattice lightsheet microscopy (tLLSM), which combines optical tiling and lattice lightsheet, and discuss the applications of tLLSM in ExM.

关键词： 3D imaging Expansion microscopy Lightsheet microscopy Super-resolution imaging Thick tissue imaging Tiling lattice lightsheet

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