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arXiv 2022年

作者： Baydin, Andrey Hayashida, Kenji Makihara, Takuma Tay, Fuyang Ma, Xiaoxuan Ren, Wei Ma, Guohong Noe, G. Timothy Katayama, Ikufumi Takeda, Jun Nojiri, Hiroyuki Cao, Shixun Bamba, Motoaki Kono, Junichiro Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States The Smalley-Curl Institute Rice University HoustonTX77005 United States Division of Applied Physics Graduate School of Engineering Hokkaido University Hokkaido Sapporo060-8628 Japan Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Physics International Center of Quantum and Molecular Structures Materials Genome Institute Shanghai University Shanghai200444 China Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama240-8501 Japan Institute for Materials Research Tohoku University Sendai980-8577 Japan The Hakubi Center for Advanced Research Kyoto University Kyoto606-8502 Japan Department of Physics I Kyoto University Kyoto606-8502 Japan PRESTO Japan Science and Technology Agency Kawaguchi332-0012 Japan Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Depending on the relative rates of coupling and dissipation, a light-matter coupled system is either in the weak- or strong-coupling regime. Here, we present a unique system where the coupling rate continuously increases with an externally applied magnetic field while the dissipation rate remains constant, allowing us to monitor a weak-to-strong coupling transition as a function of magnetic field. We observed a Rabi splitting of a terahertz magnon mode in yttrium orthoferrite above a threshold magnetic field of ∼14 T. Based on a microscopic theoretical model, we show that with increasing magnetic field the magnons transition into magnon polaritons through an exceptional point, which will open up new opportunities for in situ control of non-Hermitian systems. Copyright © 2022, The Authors. All rights reserved.

关键词： Polariton

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Radar Occupancy Prediction with Lidar Supervision while Preserving Long-Range Sensing and Penetrating Capabilities

arXiv

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arXiv 2021年

作者： Kung, Pou-Chun Wang, Chieh-Chih Lin, Wen-Chieh The Graduate Degree Program of Robotics National Yang Ming Chiao Tung University Hsinchu Taiwan The Department of Electrical and Computer Engineering National Yang Ming Chiao Tung University Taiwan The Mechanical and Mechatronics Systems Research Laboratories Industrial Technology Research Institute Hsinchu Taiwan The Department of Computer Science National Yang Ming Chiao Tung University Hsinchu Taiwan

Radar shows great potential for autonomous driving by accomplishing long-range sensing under diverse weather conditions. But radar is also a particularly challenging sensing modality due to the radar noises. Recent works have made enormous progress in classifying free and occupied spaces in radar images by leveraging lidar label supervision. However, there are still several unsolved issues. Firstly, the sensing distance of the results is limited by the sensing range of lidar. Secondly, the performance of the results is degenerated by lidar due to the physical sensing discrepancies between the two sensors. For example, some objects visible to lidar are invisible to radar, and some objects occluded in lidar scans are visible in radar images because of the radar's penetrating capability. These sensing differences cause false positive and penetrating capability degeneration, respectively. In this paper, we propose training data preprocessing and polar sliding window inference to solve the issues. The data preprocessing aims to reduce the effect caused by radar-invisible measurements in lidar scans. The polar sliding window inference aims to solve the limited sensing range issue by applying a near-range trained network to the long-range region. Instead of using common Cartesian representation, we propose to use polar representation to reduce the shape dissimilarity between long-range and near-range data. We find that extending a near-range trained network to long-range region inference in the polar space has 4.2 times better IoU than in Cartesian space. Besides, the polar sliding window inference can preserve the radar penetrating capability by changing the viewpoint of the inference region, which makes some occluded measurements seem non-occluded for a pretrained network. Copyright © 2021, The Authors. All rights reserved.

关键词： Optical radar

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Angle-resolved photoemission spectroscopy with an in situ tunable magnetic field

arXiv

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arXiv 2023年

作者： Huang, Jianwei Yue, Ziqin Baydin, Andrey Zhu, Hanyu Nojiri, Hiroyuki Kono, Junichiro He, Yu Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley–Curl Institute Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Institute for Materials Research Tohoku University Katahira 2-1-1 Sendai980-8577 Japan Department of Applied Physics Yale University New HavenCT06511 United States

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing the momentum-resolved single-particle spectral function of materials. Historically, in situ magnetic fields have been carefully avoided as they are detrimental to the control of photoelectron trajectory during the photoelectron detection process. However, magnetic field is an important experimental knob for both probing and tuning symmetry-breaking phases and electronic topology in quantum materials. In this paper, we introduce an easily implementable method for realizing an in situ tunable magnetic field at the sample position in an ARPES experiment and analyze magnetic field induced artifacts in ARPES data. Specifically, we identified and quantified three distinct extrinsic effects of a magnetic field: Constant energy contour rotation, emission angle contraction, and momentum broadening. We examined these effects in three prototypical quantum materials, i.e., a topological insulator (Bi2Se3), an iron-based superconductor (LiFeAs), and a cuprate superconductor (Pb-Bi2Sr2CuO6+x), and demonstrate the feasibility of ARPES measurements in the presence of a controllable magnetic field. Our studies lay the foundation for the future development of the technique and interpretation of ARPES measurements of field-tunable quantum phases. Copyright © 2023, The Authors. All rights reserved.

关键词： Photoelectrons

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Radio-transparent dipole antenna based on a metasurface cloak

arXiv

引用

arXiv 2021年

作者： Soric, Jason Ra'di, Younes Farfan, Diego Alù, Andrea Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712 United States Photonics Initiative Advanced Science Research Center City University of New York NY10031 United States Physics Program Graduate Center City University of New York NY10016 United States Department of Electrical Engineering City College of the City University of New York NY10031 United States

Antenna technology is at the basis of ubiquitous wireless communication systems and sensors. Radiation is typically sustained by conduction currents flowing around resonant metallic objects that are optimized to enhance efficiency and bandwidth. However, resonant conductors are prone to large scattering of impinging waves, leading to challenges in crowded antenna environments due to blockage and distortion. Metasurface cloaks have been explored in the quest of addressing this challenge by reducing antenna scattering, but with limited performance in terms of bandwidth, footprint and overall scattering reduction. Here we introduce a different route towards radio-transparent antennas, in which the cloak itself acts as the radiating element, drastically reducing the overall footprint while enhancing scattering suppression and bandwidth, without sacrificing other relevant radiation metrics compared to conventional antennas. This technique offers a new application of cloaking technology, with promising features for crowded wireless communication platforms and noninvasive sensing. © 2021, CC BY-NC-ND.

关键词： Bandwidth

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"Hall" transport of liquid crystal solitons in Couette flow

arXiv

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arXiv 2024年

作者： Coelho, Rodrigo C.V. Zhao, Hanqing Amaral, Guilherme N.C. Smalyukh, Ivan I. Telo da Gama, Margarida M. Tasinkevych, Mykola Centro de Física Teórica e Computacional Faculdade de Ciências Universidade de Lisboa Lisboa1749-016 Portugal Departamento de Física Faculdade de Ciências Universidade de Lisboa LisboaP-1749-016 Portugal Department of Physics and Soft Materials Research Center University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States International Institute for Sustainability Knotted Chiral Meta Matter Hiroshima University Higashihiroshima739-8511 Japan SOFT Group School of Science and Technology Nottingham Trent University Clifton Lane NottinghamNG11 8NS United Kingdom

Topology establishes a unifying framework for a diverse range of scientific areas including particle physics, cosmology, and condensed matter physics. One of the most fascinating manifestations of topology in the context of condensed matter is the topological Hall effect, and its relative: the Skyrmion Hall effect. Skyrmions are stable vortex-like spin configurations in certain chiral magnets, and when subject to external electric currents can drift in the transverse direction to the current. These quasi-particles are characterised by a conserved topological charge which in the Skyrmion Hall effect plays the role of electric charges in the ordinary Hall effect. Recently, it has been shown that liquid crystals endowed with chiral properties serve as an ideal testbed for the fundamental investigation of topological solitons, including their two- and three-dimensional realisations. Here, we show experimentally and numerically that three-dimensional solitons aka"torons" exhibit a Hall-like effect when driven by shear flows: the torons are deflected in the direction perpendicular to the shear plane. The experimental results are rationalised in terms of the dynamic Ericksen-Leslie equations, which predict the emergence of the transverse component of the net mass flow, the magnitude of which scales as the 3rd power of the shear rate. The perturbation analysis highlights an interplay of the viscous and chiral elastic torques as the mechanism for the emergence of net transverse currents. Numerical simulations demonstrate, however, that torons are not merely dragged by the flow but move with their own transverse speed, much larger than the average flow velocity in the transverse direction. Our findings may enable responsive microfluidic applications relying on soft topological solitons. Copyright © 2024, The Authors. All rights reserved.

关键词： Liquid crystals

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Liquid crystal torons in Poiseuille-like flows

arXiv

引用

arXiv 2024年

作者： Amaral, Guilherme N.C. Zhao, Hanqing Sedahmed, Mahmoud Campante, Tomás Smalyukh, Ivan I. Tasinkevych, Mykola Telo da Gama, Margarida M. Coelho, Rodrigo C.V. Centro de Física Teórica e Computacional Faculdade de Ciências Universidade de Lisboa Lisboa1749-016 Portugal Departamento de Física Faculdade de Ciências Universidade de Lisboa LisboaP-1749-016 Portugal Department of Physics Soft Materials Research Center University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States International Institute for Sustainability with Knotted Chiral Meta Matter Hiroshima University Higashihiroshima739-8511 Japan SOFT Group School of Science and Technology Nottingham Trent University Clifton Lane NottinghamNG11 8NS United Kingdom

Three-dimensional (3D) simulations of the structure of liquid crystal (LC) torons, topologically protected distortions of the LC director field, under material flows are rare but essential in microfluidic applications. Here, we show that torons adopt a steady-state configuration at low flow velocity before disintegrating at higher velocities, in line with experimental results. Furthermore, we show that under partial slip conditions at the boundaries, the flow induces a reversible elongation of the torons, also consistent with the experimental observations. These results are in contrast with previous simulation results for 2D skyrmions under similar flow conditions, highlighting the need for a 3D description of this LC soliton in relation to its coupling to the material flow. These findings pave the way for future studies of other topological solitons, like hopfions and heliknotons, in flowing soft matter systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Crystal structure

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Observation of the Magnonic Dicke Superradiant Phase Transition

arXiv

引用

arXiv 2024年

作者： Kim, Dasom Dasgupta, Sohail Ma, Xiaoxuan Park, Joong-Mok Wei, Hao-Tian Luo, Liang Doumani, Jacques Li, Xinwei Yang, Wanting Cheng, Di Kim, Richard H.J. Everitt, Henry O. Kimura, Shojiro Nojiri, Hiroyuki Wang, Jigang Cao, Shixun Bamba, Motoaki Hazzard, Kaden R.A. Kono, Junichiro Applied Physics Graduate Program Smalley–Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Ames National Laboratory AmesIA50011 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Physics International Center of Quantum and Molecular Structures Materials Genome Institute Shanghai University Shanghai200444 China Department of Physics National University of Singapore 117551 Singapore Department of Physics and Astronomy Iowa State University AmesIA50011 United States Smalley–Curl Institute Rice University HoustonTX77005 United States DEVCOM Army Research Laboratory-South HoustonTX77005 United States Institute for Materials Research Tohoku University Sendai980-8577 Japan Department of Physics Yokohama National University Yokohama240-8501 Japan Department of Physics and Astronomy University of California DavisCA95616 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Two-level atoms coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition when the coupling strength exceeds a critical value, entering a phase in which atomic polarization and photonic field are finite even at zero temperature and without external driving. However, this phenomenon, the superradiant phase transition (SRPT), is forbidden by a no-go theorem due to the existence of the diamagnetic term in the Hamiltonian. Here, we present spectroscopic evidence for a magnonic SRPT in ErFeO3, where the role of the photonic mode (two-level atoms) in the photonic SRPT is played by an Fe3+ magnon mode (Er3+ spins). The absence of the diamagnetic term in the Fe3+–Er3+ exchange coupling ensures that the no-go theorem does not apply. Terahertz and gigahertz magnetospectroscopy experiments revealed the signatures of the SRPT – a kink and a softening, respectively, of two spin–magnon hybridized modes at the critical point. Copyright © 2024, The Authors. All rights reserved.

关键词： Phase transitions

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Observation of current-induced switching in non-collinear antiferromagnetic IrMn3 by differential voltage measurements

arXiv

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arXiv 2021年

作者： Arpaci, Sevdenur Lopez-Dominguez, Victor Shi, Jiacheng Sánchez-Tejerina, Luis Garesci, Francesca Wang, Chulin Yan, Xueting Sangwan, Vinod K. Grayson, Matthew Hersam, Mark C. Finocchio, Giovanni Amiri, Pedram Khalili Department of Electrical and Computer Engineering Northwestern University EvanstonIL60208 United States Graduate Program in Applied Physics Northwestern University EvanstonIL60208 United States Department of Mathematical and Computer Sciences Physical Sciences and Earth Sciences University of Messina Messina98166 Italy Department of Engineering University of Messina Messina98166 Italy Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States

There is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling AFM order via spin-orbit torques, and its read-out via magnetoresistive effects. Recent studies have shown, however, that high current densities create non-magnetic contributions to resistive switching signals in AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we introduce an experimental protocol to unambiguously distinguish current-induced magnetic and nonmagnetic switching signals in AFM/HM structures, and demonstrate it in IrMn3/Pt devices. A six-terminal double-cross device is constructed, with an IrMn3 pillar placed on one cross. The differential voltage is measured between the two crosses with and without IrMn3 after each switching attempt. For a wide range of current densities, reversible switching is observed only when write currents pass through the cross with the IrMn3 pillar, eliminating any possibility of non-magnetic switching artifacts. Micromagnetic simulations support our findings, indicating a complex domain-mediated switching process. © 2021, CC BY.

关键词： Binary alloys

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Null space-based formation control with leader change possibility 19

Null space-based formation control with leader change possib...

引用

19th international Conference on Advanced Robotics, ICAR 2019

作者： Netol, Valentim Ernandes Sarcinelli-Filho, Mario Brandao, Alexandre Santos Núcleo de Especialização em Robótica Federal University of Viçosa Department of Electrical Engineering and Graduate Program on Computer Science Viçosa MG Brazil Graduate Program on Electrical Engineering Federal University of Espírito Santo Vitória - ES Brazil

ISBN: (纸本)9781728124674

This work discusses the implementation and experimentation of a control system designed to guide a multi-robot formation of one aerial and three ground robots, in a trajectory tracking task. The implementation considers three partial formations of two robots, each one associated to a virtual structure, a straight line in the 3D space with its own formation controller. Two of the partial line formations are homogeneous formations of two ground vehicles, and the third one is a heterogeneous formation, involving a ground and an aerial vehicles. All the partial formations have the same reference for position, which is one of the ground vehicles. This also allows to discuss what would happen if this ground vehicle, the reference for all the line formations, and thus for the whole formation, presents a failure, what is considered here, in connection to an escorting mission. The result is that the designed control system is effectively able to accomplish the mission, even upon a failure of the reference robot, what is validated by experimental results also discussed here. © 2019 IEEE.

关键词： Ground vehicles

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Load Manipulation by a Triangular Formation of Quadrotors

Load Manipulation by a Triangular Formation of Quadrotors

引用

international Conference on Unmanned Aircraft Systems (ICUAS)

作者： Valentim Ernandes Neto Alexandre Santos Brandão Mário Sarcinelli-Filho Graduate Program on Electrical Engineering Federal University of Espírito Santo Vitória ES Brazil Núcleo de Especialização em Robótica Department of Electrical Engineering and Graduate Program on Computer Science Federal University of Viçosa Viçosa MG Brazil

ISBN: (数字)9781728142784

ISBN: (纸本)9781728142791

This work discusses a trajectory tracking task accomplished by a group of three Bebop 2 quadrotors working cooperatively to transport a load. Such unmanned aerial vehicles (UAVs) are considered as a triangular formation, and the load, a triangle-shaped structure, is attached to them through massless flexible cables. The reason to use three quadrotors is the gain in terms of the payload capability and the stability of the load, since it is attached to three vehicles, staying vertically aligned with the center of mass of the triangle correspondent to the formation. A formation controller, actually a kinematic controller applied to a virtual massless robot correspondent to the center of mass of the triangle, is adopted, which generates reference velocities for the three UAVs, whose movement generates the movement and reshaping of the triangular formation. Then, individual dynamic compensators are adopted for each UAV, whose input is the reference velocity delivered by the formation controller. Finally, experimental results are discussed, which validate the proposal.

关键词： Vehicle dynamics Aerodynamics Atmospheric modeling Aircraft Robot kinematics Mathematical model

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