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arXiv 2020年

作者： Makihara, Takuma Hayashida, Kenji Noe, G. Timothy Li, Xinwei Peraca, Nicolas Marquez Ma, Xiaoxuan Jin, Zuanming Ren, Wei Ma, Guohong Katayama, Ikufumi Takeda, Jun Nojiri, Hiroyuki Turchinovich, Dmitry Cao, Shixun Bamba, Motoaki Kono, Junichiro Department of Physics and Astronomy Rice University HoustonTX United States Department of Electrical and Computer Engineering Rice University HoustonTX United States Division of Applied Physics Graduate School Faculty of Engineering Hokkaido University Sapporo Hokkaido060-8628 Japan Department of Physics International Center of Quantum and Molecular Structures and Materials Genome Institute Shanghai University Shanghai200444 China Terahertz Technology Innovation Research Institute Terahertz Spectrum and Imaging Technology Cooperative Innovation Center Shanghai Key Lab of Modern Optical System University of Shanghai for Science and Technology 516 JunGong Road Shanghai200093 China Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama Japan Institute for Materials Research Tohoku University Sendai Japan Fakultät für Physik Universität Bielefeld Universitätsstr. 25 Bielefeld33615 Germany Department of Physics Kyoto University Sakyo-ku Kyoto606-8502 Japan PRESTO Japan Science and Technology Agency Saitama332-0012 Japan Department of Materials Science and NanoEngineering Rice University HoustonTX United States

Exotic quantum vacuum phenomena are predicted in cavity quantum electrodynamics (QED) systems with ultrastrong light-matter interactions. Their ground states are predicted to be vacuum squeezed states with suppressed quantum fluctuations. The source of such phenomena is antiresonant terms in the Hamiltonian, yet antiresonant interactions are typically negligible compared to resonant interactions in light-matter systems. We report an unusual, ultrastrongly coupled matter-matter system of magnons that is analytically described by a unique Hamiltonian in which the relative importance of resonant and antiresonant interactions can be easily tuned and the latter can be made vastly dominant. We found a novel regime where vacuum Bloch-Siegert shifts, the hallmark of antiresonant interactions, greatly exceed analogous frequency shifts from resonant interactions. Further, we theoretically explored the system's ground state and calculated up to 5.9 dB of quantum fluctuation suppression. These observations demonstrate that magnonic systems provide an ideal platform for exploring exotic quantum vacuum phenomena predicted in ultrastrongly coupled light-matter systems. Copyright © 2020, The Authors. All rights reserved.

关键词： Hamiltonians

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Asymmetric topological pumping in nonparaxial photonics

arXiv

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arXiv 2021年

作者： Cheng, Qingqing Wang, Huaiqiang Ke, Yongguan Chen, Tao Yu, Ye Kivshar, Yuri S. Lee, Chaohong Pan, Yiming Shanghai Key Laboratory of Modern Optical System School of Optical-Electrical and Computer Engineering University of Shanghai for Science and Technology Shanghai200093 China National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing210093 China Department of Physics University of Zurich Zurich8057 Switzerland Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing School of Physics and Astronomy Sun Yat-Sen University Zhuhai Campus Zhuhai519082 China State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-Sen University Guangzhou Campus Guangzhou510275 China Nonlinear Physics Centre Research School of Physics Australian National University CanberraACT2601 Australia Physics Department Solid State Institute Technion Haifa32000 Israel

Topological photonics was initially inspired by the quantum-optical analogy between the Schrödinger equation for an electron wavefunction and the paraxial equation for a light beam. Here, we reveal an unexpected phenomenon in topological pumping observed in arrays of nonparaxial optical waveguides where the quantum-optical analogy becomes invalid. We predict theoretically and demonstrate experimentally an asymmetric topological pumping when the injected field transfers from one side of the waveguide array to the other side whereas the reverse process is unexpectedly forbidden. Our finding could open an avenue for exploring topological photonics that enables nontrivial topological phenomena and designs in photonics driven by nonparaxiality. © 2021, CC BY.

关键词： Topology

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Diamond/c-BN HEMTs for power applications: A theoretical feasibility analysis

arXiv

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arXiv 2019年

作者： Narendra, Namita Narayan, Jagdish Kim, Ki Wook Department of Electrical and Computer Engineering North Carolina State University RaleighNC27695 United States Department of Materials Science and Engineering North Carolina State University RaleighNC27695 United States Department of Physics North Carolina State University RaleighNC27695 United States

Diamond is a promising material for high-power electronic applications in both the dc and rf domains. However, the predicted advantages are yet to be realized for a number of technical challenges. In particular, n-type devices have not been feasible due to the large ionization energies and low thermodynamic solubility limits of n- dopants. Motivated by the recent advances in nonequilibrium processing, we propose and theoretically examine a diamond/c-BN HEMT that can circumvent the critical limitations. A first-principles calculation suggests the desired type-I alignment at the heterojunction of these two nearly lattice matched semiconductors. The investigation also illustrates that a large sheet carrier density in excess of 5 × 1012cm-2can be induced in the undoped diamond channel by the gate bias. A subsequent analysis of a simple prototype design indicates that the proposed device can achieve large current drive (~ 10 A/cm), low Ron(~ 0.05 mΩ Ω cm2), and high fT(~ 300 GHz) simultaneously. Copyright © 2019, The Authors. All rights reserved.

关键词： Diamonds

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Metal/BaTiO3/β-Ga2O3dielectric heterojunction diode with 5.7 MV/cm breakdown field

arXiv

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arXiv 2019年

作者： Xia, Zhanbo Chandrasekar, Hareesh Moore, Wyatt Wang, Caiyu Lee, Aidan McGlone, Joe Kalarickal, Nidhin Kurian Arehart, Aaron Ringel, Steven Yang, Fengyuan Rajan, Siddharth Electrical & Computer Engineering Ohio State University ColumbusOH43210 United States Materials Science and Engineering Ohio State University ColumbusOH43210 United States Department of Physics Ohio State University ColumbusOH43210 United States

Wide and ultra-wide band gap semiconductors can provide excellent performance due to their high energy band gap, which leads to breakdown electric fields that are more than an order of magnitude higher than conventional silicon electronics. In materials where p-type doping is not available, achieving this high breakdown field in a vertical diode or transistor is very challenging. We propose and demonstrate the use of dielectric heterojunctions that use extreme permittivity materials to achieve high breakdown field in a unipolar device. We demonstrate the integration of a high permittivity material BaTiO3with n-type β-Ga2O3to enable 5.7 MV/cm average electric field and 7 MV/cm peak electric field at the device edge, while maintaining forward conduction with relatively low on-resistance and voltage loss. The proposed dielectric heterojunction could enable new design strategies to achieve theoretical device performance limits in wide and ultrawide band gap semiconductors where bipolar doping is challenging. Copyright © 2019, The Authors. All rights reserved.

关键词： Dielectric materials

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Nonlinear planar Hall effect

arXiv

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arXiv 2019年

作者： He, Pan Zhang, Steven S.L. Zhu, Dapeng Shi, Shuyuan Heinonen, Olle G. Vignale, Giovanni Yang, Hyunsoo Department of Electrical and Computer Engineering NUSNNI National University of Singapore 117576 Singapore Materials Science Division Argonne National Laboratory LemontIL60439 United States Department of Physics and Astronomy University of Missouri ColumbiaMO65211 United States

An intriguing property of three-dimensional (3D) topological insulator (TI) is the existence of surface states with spin-momentum locking, which offers a new frontier of exploration in spintronics. Here, we report the observation of a new type of Hall effect in a 3D TI Bi2Se3 film. The Hall resistance scales linearly with both the applied electric and magnetic fields and exhibits a π/2 angle offset with respect to its longitudinal counterpart, in contrast to the usual angle offset of π/4 between the linear planar Hall effect and the anisotropic magnetoresistance. This novel nonlinear planar Hall effect originates from the conversion of a nonlinear transverse spin current to a charge current due to the concerted actions of spin-momentum locking and time reversal symmetry breaking, which also exists in a wide class of non-centrosymmetric materials with a large span of magnitude. It provides a new way to characterize and utilize the nonlinear spin-to-charge conversion in a variety of topological quantum materials. Copyright © 2019, The Authors. All rights reserved.

关键词： Locks (fasteners)

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Low Temperature Electron Microscopy of “Charge-Ordered” Phases

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Microscopy and Microanalysis 2019年第S2期25卷 934-935页

作者： Ismail El Baggari David J. Baek Benjamin H. Savitzky Michael J. Zachman Robert Hovden Lena F. Kourkoutis Department of Physics Cornell University Ithaca NY USA. School of Electrical and Computer Engineering Cornell University Ithaca NY USA. School of Applied and Engineering Physics Cornell University Ithaca NY USA. Department of Materials Science & Engineering University of Michigan Ann Arbor MI USA. Kavli Institute at Cornell for Nanoscale Science Cornell University Ithaca NY USA.

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Coexistence of magnetic orders in two-dimensional magnet CrI3

arXiv

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arXiv 2019年

作者： Niu, Ben Su, Tang Francisco, Brian A. Ghosh, Subhajit Kargar, Fariborz Huang, Xiong Lohmann, Mark Li, Junxue Xu, Yadong Taniguchi, Takashi Watanabe, Kenji Wu, Di Balandin, Alexander Shi, Jing Cui, Yong-Tao National Laboratory of Solid State Microstructures Department of Materials Science and Engineering Jiangsu Key Laboratory for Artificial Functional Materials Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China Department of Physics and Astronomy University of California RiversideCA92521 United States International Center for Quantum Materials School of Physics Peking University Beijing100871 China Department of Electrical and Computer Engineering University of California RiversideCA92521 United States Department of Materials Science and Engineering University of California RiversideCA92521 United States National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

The magnetic properties in two-dimensional van der Waals materials depend sensitively on structure. CrI3, as an example, has been recently demonstrated to exhibit distinct magnetic properties depending on the layer thickness and stacking order. Bulk CrI3 is ferromagnetic (FM) with a Curie temperature of 61 K and a rhombohedral layer stacking, while few-layer CrI3 has a layered antiferromagnetic (AFM) phase with a lower ordering temperature of 45 K and a monoclinic stacking. In this work, we use cryogenic magnetic force microscopy to investigate CrI3 flakes in the intermediate thickness range (25 – 200 nm) and find that the two types of magnetic orders hence the stacking orders can coexist in the same flake, with a layer of ~13 nm at each surface being in the layered AFM phase similar to few-layer CrI3 and the rest in the bulk FM phase. The switching of the bulk moment proceeds through a remnant state with nearly compensated magnetic moment along the c-axis, indicating formation of c-axis domains allowed by a weak interlayer coupling strength in the rhombohedral phase. Our results provide a comprehensive picture on the magnetism in CrI3 and point to the possibility of engineering magnetic heterostructures within the same material. Copyright © 2019, The Authors. All rights reserved.

关键词： Magnets

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Effect of synthesis conditions on the electrical resistivity of TiSe2

引用

Physical Review materials 2019年第8期3卷 084005-084005页

作者： Jaime M. Moya C.-L. Huang Jesse Choe Gelu Costin Matthew S. Foster E. Morosan Applied Physics Program Rice University Houston Texas 77005 USA Department of Physics and Astronomy Rice University Houston Texas 77005 USA Rice Center for Quantum Materials Rice University Houston Texas 77005 USA Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Department of Earth Environmental and Planetary Sciences Rice University Houston Texas 77005 USA

Dilute impurities and growth conditions can drastically affect the transport properties of TiSe2, especially below the charge-density-wave transition. In this paper, we discuss the effects of cooling rate, annealing time, and annealing temperature on the transport properties of TiSe2: slow cooling polycrystalline TiSe2 postsynthesis drastically increases the low-temperature resistivity, which is in contrast to the metallic behavior of single-crystalline TiSe2 attributed to charge doping from the residual iodine transport agent. A logarithmic increase of resistivity upon cooling and negative magnetoresistance with a sharp cusp around zero field are observed for the first time for the polycrystalline TiSe2 samples, pointing to weak-localization effects due to low dimensionality. Annealing at low temperatures has a similar, but less drastic effect. Furthermore, rapid quenching of the polycrystalline samples from high temperatures freezes in disorder, leading to a decrease in the low-temperature resistivity.

关键词： Charge density waves Disordered systems Transition metal dichalcogenides Annealing Crystal growth Resistivity measurements

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Broadband Scanning Microwave Microscopy of a Biological Cell with Unprecedented Image Quality and Signal-to-Noise Ratio

Broadband Scanning Microwave Microscopy of a Biological Cell...

引用

Microwave, MTT-S International Symposium

作者： Xin Jin Marco Farina Xiaopeng Wang Gianluca Fabi Xuanhong Cheng James C. M. Hwang Department of Electrical and Computer Engineering Lehigh University Bethlehem PA USA Dipartimento di Ingegneria dell’Informazione Università Politecnica delle Marche Ancona Italy Dept. of Materials Science and Engineering and Dept. of Bioengineering Lehigh University PA USA

A broadband scanning microwave microscope (SMM) was developed by modifying both the hardware and software of a narrowband commercial SMM. Using the broadband SMM, images of a Jurkat human lymphocyte cell were acquired over 128 × 128 pixels at 201 frequencies from 1 GHz to 9 GHz, all in 20 min. The acquired broadband signals allowed Fourier transformation for time-gated postprocessing of the SMM data with unprecedented image quality and signal-to-noise ratio. The broadband SMM can enable microwave spectroscopy and 3D tomography of intracellular structures in a live cell.

关键词： Broadband communication Signal to noise ratio Narrowband Probes Microwave imaging Microwave circuits

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A biometric based medical information system for the identification of comorbidity in Covid-19 patients

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AIP Conference Proceedings 2021年第1期2387卷

作者： V. Kumaresan K. Punitha S. Ragupathy B. Priestly Shan T. Gunasekaran 1Department of Electrical and Electronics Engineering Kongu Engineering College Perundurai Tamilnadu India 2School of Computer Science and Engineering Vellore Institute of Technology Chennai Tamil Nadu India 3Department of Electrical and Electronics Engineering SSM College of Engineering Komarapalayam Namakkal Tamil Nadu India 4Professor and Dean - Academic Affairs Chandigarh University Mohali Punjab India 5Program Director - Telecommunications University of Technology and Applied Sciences Higher College of Technology Muscat Sultanate of Oman

Medical information System provides the best way to collect patient’s medical information. It helps the doctors to retrieve the patient’s previous medical history very faster and able to provide suitable treatment quickly. To keep medical information of a patient securely is a difficult task. Many MQTT algorithms have been developed to provide security for the patients information. The sensitive medical information of a patient can also be protected by using biometric technology. Internet of Thing (IoT) technology used to send the medical information to the doctor like blood group, BP value, cholesterol level and heart rate level. The proposed system helps to provide the comorbidity details of the Covid-19 infected patient’s to doctors mobile phone. It also takes the current health details of the patients like temperature, respiratory rate and heart beat rate. By considering the past and present medical data of the Covid-19 patients , this system recommends the type of treatment to be given for Covid-19 infected patients.

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