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arXiv 2023年

作者： Karmakar, Annesha Pal, Anikesh Kumar, G. Anil Bhavika Anand, V. Tyagi, Mohit Nuclear Engineering and Technology Program Indian Institute of Technology Kanpur India Department of Mechanical Engineering Indian Institute of Technology Kanpur India Radiation Detectors and Spectroscopy Laboratory Department of Physics Indian Institute of Technology Roorkee India Technical Physics Division Bhabha Atomic Research Centre Mumbai India

This study shows an implementation of neutron-gamma pulse shape discrimination (PSD) using a two-dimensional convolutional neural network. The inputs to the network are snapshots of the unprocessed, digitized signals from a BC501A detector. By exposing a BC501A detector to a Cf-252 source, neutron and gamma signals were collected to create a training dataset. The realistic datasets were created using a data-driven approach for labeling the digitized signals, having classified snapshots of neutron and gamma pulses. Our algorithm was able to successfully differentiate neutrons and gammas with similar accuracy as the CI approach. Additionally, the independent dataset accuracy for our suggested 2D CNN-based PSD approach is 99%. In contrast to the traditional charge integration method, our suggested algorithm with data augmentation, is capable of extracting features from snapshots of the raw data based on the signal structures, making it computationally more efficient and also appropriate for other types of neutron detectors. Copyright © 2023, The Authors. All rights reserved.

关键词： Neutrons

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Quantum simulation of an extended Dicke model with a magnetic solid

Communications Materials

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Communications Materials 2024年第1期5卷 1-9页

作者： Marquez Peraca, Nicolas Li, Xinwei Moya, Jaime M. Hayashida, Kenji Kim, Dasom Ma, Xiaoxuan Neubauer, Kelly J. Fallas Padilla, Diego Huang, Chien-Lung Dai, Pengcheng Nevidomskyy, Andriy H. Pu, Han Morosan, Emilia Cao, Shixun Bamba, Motoaki Kono, Junichiro Department of Physics and Astronomy Rice University HoustonTX United States Department of Physics California Institute of Technology PasadenaCA United States Applied Physics Graduate Program Smalley–Curl Institute Rice University HoustonTX United States Division of Applied Physics Graduate School of Engineering Hokkaido University Hokkaido Japan Department of Electrical and Computer Engineering Rice University HoustonTX United States Department of Physics International Center of Quantum and Molecular Structures and Materials Genome Institute Shanghai University Shanghai China Department of Physics and Center for Quantum Frontiers of Research and Technology National Cheng Kung University Tainan Taiwan Department of Chemistry Rice University HoustonTX United States Department of Physics I Kyoto University Kyoto Japan The Hakubi Center for Advanced Research Kyoto University Kyoto Japan PRESTO Japan Science and Technology Agency Saitama Japan Department of Physics Yokohama National University Yokohama Japan Department of Materials Science and NanoEngineering Rice University HoustonTX United States

The Dicke model describes the cooperative interaction of an ensemble of two-level atoms with a single-mode photonic field and exhibits a quantum phase transition as a function of light–matter coupling strength. Extending this model by incorporating short-range atom–atom interactions makes the problem intractable but is expected to produce new physical phenomena and phases. Here, we simulate such an extended Dicke model using a crystal of ErFeO3, where the role of atoms (photons) is played by Er3+ spins (Fe3+ magnons). Through terahertz spectroscopy and magnetocaloric effect measurements as a function of temperature and magnetic field, we demonstrated the existence of a novel atomically ordered phase in addition to the superradiant and normal phases that are expected from the standard Dicke model. Further, we elucidated the nature of the phase boundaries in the temperature–magnetic-field phase diagram, identifying both first-order and second-order phase transitions. These results lay the foundation for studying multiatomic quantum optics models using well-characterized many-body solid-state systems. © The Author(s) 2024.

关键词： Atoms

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Ultrafast measurements of the interfacial spin Seebeck effect in Au and rare-earth iron-garnet bilayers

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Physical Review Materials 2021年第7期5卷 074401-074401页

作者： Víctor H. Ortiz Michael J. Gomez Yawen Liu Mohammed Aldosary Jing Shi Richard B. Wilson Department of Mechanical Engineering and Materials Science and Engineering Program University of California Riverside California 92521 USA Department of Physics and Astronomy Program University of California Riverside California 92521 USA

We investigate picosecond spin currents across Au/iron-garnet interfaces in response to ultrafast laser heating of the electrons in the Au film. In the picoseconds after optical heating, interfacial spin currents occur due to an interfacial temperature difference between electrons in the metal and magnons in the insulator. We report measurements of this interfacial longitudinal spin Seebeck effect between Au and rare-earth iron-garnet insulators, i.e., RE3Fe5O12, where RE is Y, Eu, Tb, Tm. By systematically varying the rare-earth element, we modify the total magnetic moment of the iron garnet. We use time-domain thermoreflectance measurements to characterize the thermal response of the bilayer to ultrafast optical heating. We use time-resolved magneto-optic Kerr effect measurements of the Au layer to measure the time evolution of spin accumulation in the Au film. Replacing Y with other rare earths enhances the electron-magnon conductance Ge−m at the Au iron-garnet interface by as much as a factor of 3. The electron-magnon conductance does not follow the trend of either the total magnetization of the iron garnet or the magnetic moment of the rare earth.

关键词： Magneto-optical Kerr effect Magnons Spin Seebeck effect Spin polarization Ultrafast magnetic effects

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Development of a Pixelated BaF2 Test Bed for Timing Applications

Development of a Pixelated BaF2 Test Bed for Timing Applicat...

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2022 IEEE Nuclear Science Symposium, Medical Imaging Conference, and Room Temperature Semiconductor Detector Conference, IEEE NSS MIC RTSD 2022

作者： Jordan, Tyler A. Andrews, Madison T. Johnson, Christopher R. McKigney, Edward A. Stange, Sy Vetter, Kai Los AlamosNM87545 United States Los AlamosNM87545 United States University of California Department of Nuclear Engineering BerkeleyCA94720 United States Lawrence Berkeley National Laboratory Applied Nuclear Physics Program BerkeleyCA94720 United States

ISBN: (纸本)9781665488723

Prototype pixelated BaF2 detectors for timing applications have been assembled using state-of-the-art commercial off-the-shelf components. 64 square rods of pure BaF2 (4.6 mm × 4.6 mm × 30 mm) are air-coupled in an 8 × 8 array to a Photonis XP85112 Planacon multianode microchannel plate photomultiplier tube;shortpass optical transmission interference filters may be inserted between the crystal array and photodetector to suppress the slow, self-trapped exciton luminescence. Three filter variants with different long wavelength cutoffs were tested experimentally, and the performance of each filter is assessed. The results of these and upcoming detector characterization exeriments will ascertain how well new technologies can leverage the unique timing properties of BaF2 in a practical system, and provide quantitative guidance for effective continued development. © 2022 IEEE.

关键词： barium fluoride (BaF2) multianode microchannel plate photomultiplier tube (MCP-PMT) optical transmission interference filter

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Interfacial thermal transport in spin caloritronic material systems

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Physical Review Materials 2021年第11期5卷 114403-114403页

作者： Frank Angeles Qiyang Sun Victor H. Ortiz Jing Shi Chen Li Richard B. Wilson Department of Mechanical Engineering and Materials Science and Engineering Program University of CaliforniaRiverside California 92521 USA Department of Physics and Astronomy Program University of California Riverside California 92521 USA

Interfaces often govern the thermal performance of nanoscale devices and nanostructured materials. As a result, accurate knowledge of thermal interface conductance is necessary to model the temperature response of nanoscale devices or nanostructured materials to heating. Here, we report the thermal boundary conductance between metals and insulators that are commonly used in spin-caloritronic experiments. We use time-domain thermoreflectance to measure the interface conductance between metals such as Au, Pt, Ta, Cu, and Al with garnet and oxide substrates, e.g., NiO, yttrium iron garnet (YIG), thulium iron garnet (TmIG), Cr2O3, and sapphire. We find that, at room temperature, the interface conductance in these types of material systems range from 50 to 300MWm−2K−1. We also measure the interface conductance between Pt and YIG at temperatures between 80 and 350 K. At room temperature, the interface conductance of Pt/YIG is 170MWm−2K−1 and the Kapitza length is ∼40 nm. A Kapitza length of 40 nm means that, in the presence of a steady-state heat current, the temperature drop at the Pt/YIG interface is equal to the temperature drop across a 40-nm-thick layer of YIG. At 80 K, the interface conductance of Pt/YIG is 60MWm−2K−1, corresponding to a Kapitza length of ∼300 nm.

关键词： Thermal conductivity

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Ternary system approach in separation and purification of biodiesel fuel: An organised review

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Journal of Molecular Liquids 2024年 415卷

作者： Adama, Kenneth Kennedy Anani, Osikemekha Anthony Ukhurebor, Kingsley Eghonghon Isaac, Oamen Festus Aigbe, Uyiosa Osagie Hossain, Ismail Aluyor, Emmanuel Osikhuemeh Audu, Kimble Thomas Okpo Department of Chemical Engineering Faculty of Engineering Edo State University Edo State Uzairue Nigeria Laboratory for Ecotoxicology and Hydrobiology Department of Animal and Environmental Biology Delta State University Abraka Delta State Nigeria Department of Physics Faculty of Science Edo State University Edo State Uzairue Nigeria Department of Mechanical Engineering Faculty of Engineering Edo State University Uzairue Edo State Nigeria Department of Mathematics and Physics Faculty of Applied Sciences Cape Peninsula University of Technology Cape Town South Africa Department of Nuclear and Renewable Energy Ural Federal University Yekaterinburg620002 Russia Department of Chemical Engineering Faculty of Engineering University of Benin Edo State Benin-City Nigeria

Application of a ternary system (TS) approach involving ternary phase diagrams from liquid-–liquid equilibrium (LLE) data can assist in highlighting constituent components in biodiesel (BD) systems at investigated conditions, thereby improving the purification process. The LLE system is a mass transfer operation in which a liquid solution is contacted with a second immiscible or nearly immiscible liquid selected preferentially to remove desired components based on the solubilities of the components and their chemical differences. Different sources of feedstock for BD production are presented, as well as highlighting the necessity for enhanced feedstock quality to obtain high-quality BD. Different TS studies and approaches over the last few decades are enumerated and discussed. Furthermore, different local composition modelling approaches to the study of TS in BD are presented, highlighting the importance of component phase distribution within the ternary BD system for optimisation of the purification process and validation of experimental results based on simulated models. The ternary approach method can serve as a potential means for designing efficient separation systems that optimise BD purification after the transesterification reaction, thereby improving efficiency, material and operational cost reduction, and the elimination of wastewater generation. In this regard, this paper precisely reviews the separation and purification of BD using TS approaches. © 2024 Elsevier B.V.

关键词： Ternary systems

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Ab initio phonon transport across grain boundaries in graphene using machine learning based on small dataset

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Physical Review Materials 2022年第4期6卷 044004-044004页

作者： Amirreza Hashemi Ruiqiang Guo Keivan Esfarjani Sangyeop Lee Computational Modeling and Simulation Program University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Department of Mechanical and Aerospace Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Materials Science and Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Physics University of Virginia Charlottesville Virginia 22904 USA Department of Physics and Astronomy University of Pittsburgh Pittsburgh Pennsylvania 15261 USA

Establishing the structure-property relationship for grain boundaries (GBs) is critical for developing next-generation functional materials but has been severely hampered due to its extremely large configurational space. Atomistic simulations with low computational cost and high predictive power are strongly desirable, but the conventional simulations using empirical interatomic potentials and density functional theory suffer from the lack of predictive power and high computational cost, respectively. A machine learning interatomic potential (MLIP) recently emerged but often requires extensive size of the training dataset, making it a less feasible approach. Here, we demonstrate that an MLIP trained with a rationally designed small training dataset can predict thermal transport across GBs in graphene with ab initio accuracy at an affordable computational cost. We employed a rational approach based on the structural unit model to find a small set of GBs that can represent the entire configurational space and thus can serve as a cost-effective training dataset for the MLIP. Only 5 GBs were found to be enough to represent the entire configurational space of graphene GBs. Using the atomistic Green's function approach and the MLIP, we revealed that the structure-thermal resistance relation in graphene does not follow the common understanding that large dislocation density causes larger thermal resistance. In fact, thermal resistance is nearly independent of dislocation density at room temperature and is higher when the dislocation density is small at sub-room temperature. We explain this intriguing behavior with the buckling near a GB causing a strong scattering of flexural phonon modes. In this paper, we show that a machine learning technique combined with conventional wisdom (e.g., structural unit model) can extend the recent success of ab initio thermal transport simulation, which has been mostly limited to single crystals, to complex yet practically important polycry

关键词： Phonons Graphene Landauer formula Machine learning

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Evidence of magnetoelectronic electromagnon mediated transport in flexoelectronic heterostructures

arXiv

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arXiv 2023年

作者： Katailiha, Anand Lou, Paul C. Bhardwaj, Ravindra G. Beyermann, Ward P. Kumar, Sandeep Department of Mechanical Engineering University of California RiversideCA92521 United States Department of Physics and Astronomy University of California RiversideCA92521 United States Materials Science and Engineering Program University of California RiversideCA92521 United States

The superposition of atomic vibrations and flexoelectronic effect gives rise to a cross correlation between free charge carriers and temporal magnetic moment of phonons in conducting heterostructures under an applied strain gradient. The resulting dynamical coupling is expected to give rise to quasiparticle excitations called as magnetoelectronic electromagnon that carries electronic charge and temporal magnetic moment. Here, we report experimental evidence of magnetoelectronic electromagnon in the freestanding degenerately doped p-Si based heterostructure thin film samples. These quasiparticle excitations give rise to long-distance (>100µm) spin transport;demonstrated using spatially modulated transverse magneto-thermoelectric and non-local resistance measurements. The magnetoelectronic electromagnons are non-reciprocal and give rise to large magnetochiral anisotropy (0.352 A-1T-1) that diminishes at lower temperatures. The superposition of non-reciprocal magnetoelectronic electromagnons gives rise to longitudinal and transverse modulations in charge carrier density, spin density and magnetic moment;demonstrated using the Hall effect and edge dependent magnetoresistance measurements, which can also be called as inhomogeneous magnetoelectronic multiferroic effect. These quasiparticle excitations are analogues to photons where time dependent polarization and temporal magnetic moment replaces electric and magnetic field, respectively and most likely topological because it manifests topological Nernst effect. Hence, the magnetoelectronic electromagnon can potentially give rise to quantum interference and entanglement effects in conducting solid state system at room temperature in addition to efficient spin transport. © 2023, CC BY.

关键词： Magnetic moments

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Thickness Dependent Sensitivity of GAGG:Ce Scintillation detectors for Thermal Neutrons: GEANT4 Simulations and Experimental Measurements

arXiv

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arXiv 2023年

作者： Karmakar, Annesha Kumar, G. Anil Tyagi, Mohit Pal, Anikesh Nuclear Engineering and Technology Program Indian Institute of Technology Kanpur India Radiation Detectors and Spectroscopy Laboratory Department of Physics Indian Institute of Technology Roorkee India Technical Physics Division Bhabha Atomic Research Centre Mumbai India Department of Mechanical Engineering Indian Institute of Technology Kanpur India

In the present work, we report extensive GEANT4 simulations in order to study the dependence of sensitivity of GAGG:Ce scintillation crystal based detector on thickness of the crystal. All the simulations are made considering a thermalised Am-Be neutron source. The simulations are validated, qualitatively and quantitatively, by comparing the simulated energy spectra and sensitivity values with those obtained from experimental measurements carried out using two different thicknesses of the crystal from our own experiment (0.5mm and 3mm) and validated with three other thicknesses (0.01mm, 0.1 mm and 1 mm) from literature [1]. In this study, we define sensitivity of GAGG:Ce as the ratio of area under 77 keV sum peak to 45 keV peak. The present studies clearly confirm that, while it requires about 0.1 mm thickness for the GAGG:Ce crystal to fully absorb thermal neutrons, it requires about 3 mm to fully absorb the thermal neutron induced events. Further, we propose an equation, that can be used to estimate the thickness of the GAGG:Ce crystal directly from the observed sensitivity of the GAGG:Ce crystal. This equation could be very useful for the neutron imaging community for medical and space applications, as well as for manufactures of cameras meant for nuclear security purposes. Copyright © 2023, The Authors. All rights reserved.

关键词： Binary alloys

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Reducing Effective System Dimensionality with Long-Range Collective Dipole-Dipole Interactions

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Physical Review Letters 2024年第17期132卷 173803-173803页

作者： Ashwin K. Boddeti Yi Wang Xitlali G. Juarez Alexandra Boltasseva Teri W. Odom Vladimir Shalaev Hadiseh Alaeian Zubin Jacob Elmore Family School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA Birck Nanotechnology Center Purdue University West Lafayette Indiana 47907 USA Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Department of Chemistry Northwestern University Evanston Illinois 60208 USA School of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA

Dimensionality plays a crucial role in long-range dipole-dipole interactions (DDIs). We demonstrate that a resonant nanophotonic structure modifies the apparent dimensionality in an interacting ensemble of emitters, as revealed by population decay dynamics. Our measurements on a dense ensemble of interacting quantum emitters in a resonant nanophotonic structure with long-range DDIs reveal an effective dimensionality reduction to d¯=2.20(12), despite the emitters being distributed in 3D. This contrasts with the homogeneous environment, where the apparent dimension is d¯=3.00. Our work presents a promising avenue to manipulate dimensionality in an ensemble of interacting emitters.

关键词： Light-matter interaction Long-range interactions Metamaterials Optics & lasers Photonics Plasmonics Quantum optics

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