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Investigation of Optical Properties of Diamond Substrates Grown by Microwave Plasma Enhanced Chemical Vapour Deposition Method

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SSRN

SSRN 2023年

作者： Upadhyay, Khyati Dasadia, Abhay K. Bhatt, Sandip V. Deshpande, M.P. Faculty of Science A. D. Patel Institute of Technology C.V.M University Gujarat New Vallabh Vidyanagar388121 India Department of Applied and Interdisciplinary Sciences Sardar Patel University Vallabh Vidyanagar388 120 India Department of Physics Sardar Patel University Vallabh Vidyanagar388 120 India

Synthetic single crystal diamonds (SCDs) offer unrivalled hardness, a wide range of optical transparency and supremely high thermal conductivity. They are reliable materials to be a part of devices run at high frequency, temperature and power. Adequate synthesis methods for high-quality SCDs plays a crucial role in maximizing their potential applications. To achieve this, the growth strategy for high-quality single crystal diamonds makes use of the welding material to minimize the accumulation of graphitic carbons at the bottom of the diamond seeds. This approach reduces the thermal contact resistance at the interface between diamond seeds and the molybdenum holder. By employing the welding method, high quality diamond substrates (plates) were grown and evaluated for their optical properties using Raman, UV-Vis and FT-IR spectroscopic techniques. Obtained results showed that in Raman spectra, peaks near 1332 cm−1 called as first order Raman peaks with no observable peaks in the region 1500 cm-1–1550 cm-1 is generally considered as strong evidence for the growth of ‘pure’ diamond phase with no non-diamond components present. Grown single crystal diamonds exhibit high transmittance (>70%) and absorption at 280 nm. The FT-IR spectrum reveals peaks at 670 cm-1 and 1470 cm-1, which are attributed to nitrogen impurities. Calculations demonstrate an average absorption coefficient of 1.1 cm-1, indicating the high quality of grown SCDs with nitrogen impurities © 2023, The Authors. All rights reserved.

关键词： Optical properties

Polaronic and Mott insulating phase of layered magnetic vanadium trihalide VCl3

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arXiv 2023年

作者： Mastrippolito, Dario Camerano, Luigi Swiatek, Hanna Šmíd, Břetislav Klimczuk, Tomasz Ottaviano, Luca Profeta, Gianni Department of Physical and Chemical Sciences University of L’Aquila Via Vetoio L’Aquila67100 Italy Faculty of Applied Physics and Mathematics Gdansk University of Technology Gdansk Poland Advanced Materials Center Gdansk University of Technology Gdansk Poland Charles University Faculty of Mathematics and Physics Department of Surface and Plasma Science V Holešovičkách 2 Prague 8180 00 Czech Republic CNR-SPIN L’Aquila Via Vetoio L’Aquila67100 Italy

Two-dimensional (2D) van der Waals (vdW) magnetic 3d-transition metal trihalides are a new class of functional materials showing exotic physical properties useful for spintronic and memory storage applications. In this article, we report the synthesis and electromagnetic characterization of single-crystalline vanadium trichloride, VCl3, a novel 2D layered vdW Mott insulator, which has a rhombohedral structure (R3, No. 148) at room temperature. VCl3 undergoes a structural phase transition at 103 K and a subsequent antiferromagnetic transition at 21.8 K. Combining core levels and valence bands x-ray photoemission spectroscopy (XPS) with first-principles density functional theory (DFT) calculations, we demonstrate the Mott Hubbard insulating nature of VCl3 and the existence of electron small 2D magnetic polarons localized on V atom sites by V-Cl bond relaxation. The polarons strongly affect the electromagnetic properties of VCl3 promoting the occupation of dispersion-less spin-polarized V-3d a1g states and band inversion with eg states. Within the pola- ′ ronic scenario, it is possible to reconcile different experimental evidences on vanadium trihalides, suggesting that also VI3 hosts polarons. Our results highlight the complex physical behavior of this class of crystals determined by charge trapping, lattice distronsions, correlation effects, mixed valence states, and magnetic states. © 2023, CC BY-NC-SA.

关键词： Chlorine compounds

Antiferromagnetic Hysteresis above the Spin Flop Field

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arXiv 2021年

作者： Grzybowski, M.J. Schippers, C.F. Gomonay, O. Rubi, K. Bal, M.E. Zeitler, U. Koziol-Rachwal, A. Szpytma, M. Janus, W. Kurowska, B. Kret, S. Gryglas-Borysiewicz, M. Koopmans, B. Swagten, H.J.M. Department of Applied Physics Eindhoven University of Technology PO Box 513 Eindhoven5600 MB Netherlands Faculty of Physics University of Warsaw Pasteura 5 Warsaw Poland Institute of Physics Johannes Gutenberg-University Mainz Mainz55128 Germany Radboud University Nijmegen6525 ED Netherlands Faculty of Physics and Applied Computer Science AGH University of Science and Technology Kraków30-059 Poland Institute of Physics Polish Academy of Sciences Lotników 32/46 Warsaw Poland

Magnetocrystalline anisotropy is essential in the physics of antiferromagnets and commonly treated as a constant, not depending on an external magnetic field. However, we demonstrate that in CoO the anisotropy should necessarily depend on the magnetic field, which is shown by the spin Hall magnetoresistance of the CoO | Pt device. Below the Néel temperature CoO reveals a spin-flop transition at 240 K at 7.0 T, above which a hysteresis in the angular dependence of magnetoresistance unexpectedly persists up to 30 T. This behavior is shown to agree with the presence of the unquenched orbital momentum, which can play an important role in antiferromagnetic spintronics. © 2021, CC BY.

关键词： Magnetocrystalline anisotropy

Valley-Polarized Quantum Hall Phase in a Strain-Controlled Dirac System

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Physical Review Letters 2024年第16期132卷 166601-166601页

作者： G. Krizman J. Bermejo-Ortiz T. Zakusylo M. Hajlaoui T. Takashiro M. Rosmus N. Olszowska J. J. Kołodziej G. Bauer Y. Guldner G. Springholz L.-A. de Vaulchier Institut für Halbleiter und Festkörperphysik Johannes Kepler Universität Altenberger Strasse 69 4040 Linz Austria Laboratoire de Physique de l’Ecole normale supérieure ENS Université PSL CNRS Sorbonne Université 24 rue Lhomond 75005 Paris France National Synchrotron Radiation Centre SOLARIS Jagiellonian University Czerwone Maki 98 30-392 Krakow Poland Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University 30-348 Krakow Poland

In multivalley systems, the valley pseudospin offers rich physics going from encoding of information by its polarization (valleytronics), to exploring novel phases of matter when its degeneracy is changed. Here, by strain engineering, we reveal fully valley-polarized quantum Hall phases in the Pb1−xSnxSe Dirac system. Remarkably, when the valley energy splitting exceeds the fundamental band gap, we observe a “bipolar quantum Hall phase,” heralded by the coexistence of hole and electron chiral edge states at distinct valleys in the same quantum well. This suggests that spatially overlaid counterpropagating chiral edge states emerging at different valleys do not interfere with each other.

关键词： Edge states Integer quantum Hall effect Magneto-optics Magnetotransport Topological materials Valley degrees of freedom Valleytronics

Generative Artificial Intelligence (GAI) for Mobile Communications: A Diffusion Model Perspective

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arXiv 2024年

作者： Xu, Xiaoxia Mu, Xidong Liu, Yuanwei Xing, Hong Liu, Yue Nallanathan, Arumugam The School of Electronic Engineering and Computer Science Queen Mary University of London LondonE1 4NS United Kingdom Queen's University Belfast BelfastBT3 9DT United Kingdom The Department of Electronic Engineering Kyung Hee University Gyeonggi-do Yongin-si17104 Korea Republic of Guangzhou511453 China The Department of ECE The Hong Kong University of Science and Technology Hong Kong The Faculty of Applied Sciences Macao Polytechnic University China

This article targets at unlocking the potentials of a class of prominent generative artificial intelligence (GAI) method, namely diffusion model (DM), for mobile communications. First, a DM-driven communication architecture is proposed, which introduces two key paradigms, i.e., conditional DM and DM-driven deep reinforcement learning (DRL), for wireless data generation and communication management, respectively. Then, we discuss the key advantages of DM-driven communication paradigms. To elaborate further, we explore DM-driven channel generation mechanisms for channel estimation, extrapolation, and feedback in multiple-input multiple-output (MIMO) systems. We showcase the numerical performance of conditional DM using the accurate DeepMIMO channel datasets, revealing its superiority in generating high-fidelity channels and mitigating unforeseen distribution shifts in sophisticated scenes. Furthermore, several DM-driven communication management designs are conceived, which is promising to deal with imperfect channels and task-oriented communications. To inspire future research developments, we highlight the potential applications and open research challenges of DM-driven communications. Code is available at https://***/xiaoxiaxusummer/GAI_COMM/. Copyright © 2024, The Authors. All rights reserved.

关键词： Channel estimation

Recent Developments within The Cosmic Ray Extremely Distributed Observatory (CREDO)

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arXiv 2024年

作者： Alvarez-Castillo, David Homola, Piotr Sushchov, Oleksandr Stasielak, Jaroslaw Stuglik, Slawomir Góra, Dariusz Nazari, Vahab Oancea, Cristina Granja, Carlos Beznosko, Dmitriy Zabari, Noemi Gupta, Alok C. Hnatyk, Bohdan Mozgova, Alona Kasztelan, Marcin Bielewicz, Marcin Kovacs, Peter Lozowski, Bartosz Medvedev, Mikhail V. Miszczyk, Justyna Bibrzycki, Lukasz Niedźwiecki, Michal Smelcerz, Katarzyna Hachaj, Tomasz Piekarczyk, Marcin Pawlik, Maciej Rzecki, Krzysztof Rosas, Matías Smolek, Karel Svanidze, Manana Beradze, Revaz Tursunov, Arman Wibig, Tadeusz Zamora-Saa, Jilberto Poncyljusz, Bozena Medrala, Justyna Opila, Gabriela Pryga, Jerzy Ruimi, Ophir Cahuantzi, Mario Rodriguez Institute of Nuclear Physics Polish Academy of Sciences Radzikowskiego 152 Kraków31-342 Poland ADVACAM 12 Prague17000 Czech Republic Clayton State University MorrowGA United States Juliusza Slowackiego 24 Rzeszów35-069 Poland Manora Peak Nainital263001 India Astronomical Observatory of Taras Shevchenko National University of Kyiv Kyiv04053 Ukraine National Centre for Nuclear Research Andrzeja Soltana 7 Świerk Otwock05-400 Poland Institute for Particle and Nuclear Physics Wigner Research Centre for Physics 1121 Konkoly-Thege Miklós út Budapest29-33 Hungary Faculty of Natural Sciences University of Silesia in Katowice Bankowa 9 Katowice40-007 Poland Department of Physics and Astronomy University of Kansas LawrenceKS66045 United States Laboratory for Nuclear Science Massachusetts Institute of Technology CambridgeMA02139 United States Department of Computer Science Cracow University of Technology Warszawska 24 Kraków31-155 Poland ACC Cyfronet AGH-UST Kraków30-950 Poland AGH University of Science and Technology Mickiewicz Ave. Kraków30-059 Poland Liceo 6 Francisco Bauzá Lucas Obes 896 Montevideo11700 Uruguay Institute of Experimental and Applied Physics Czech Technical University in Prague Husova 240/5 Prague 1110 00 Czech Republic E. Andronikashvili Institute of Physics under Tbilisi State University 6 Tamarashvili St. Tbilisi0186 Georgia Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic University of Lódź Faculty of Physics and Applied Informatics 90-236 Lódź Pomorska 149/153 Poland Universidad Andres Bello Departamento de Ciencias Fisicas Facultad de Ciencias Exactas Avenida Republica 498 Santiago Chile Faculty of Physics University of Warsaw Warsaw02-093 Poland Faculty of Physics and Applied Computer Science AGH University of Science and Technology Mickiewicz Ave. Kraków30-059 Poland Pedagogical University of Krakow Institute of Computer Science ul. Podchorąych Krak

This contribution presents the recent research developments within the Cosmic Ray Extremely Distributed Observatory (CREDO) in the search for resolution of various scientific puzzles, ranging from fundamental physical questions to applications like the determination of earthquake precursors. The state-of-the art theoretical, numerical and computational aspects of these phenomena are addressed, as well as recent experimental developments for detection. © 2024, CC BY.

关键词： Cosmic rays

HERMES: Holographic Equivariant neuRal network model for Mutational Effect and Stability prediction

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arXiv 2024年

作者： Visani, Gian Marco Pun, Michael N. Galvin, William Daniel, Eric Borisiak, Kevin Wagura, Utheri Nourmohammad, Armita Department of Computer Science and Engineering University of Washington Seattle United States Department of Physics University of Washington 3910 15th Avenue Northeast SeattleWA98195 United States Department of Physics Massachusetts Institute of Technology 182 Memorial Dr CambridgeMA02139 United States Department of Applied Mathematics University of Washington Seattle United States Fred Hutchinson Cancer Research Center 1100 Fairview ave N SeattleWA98109 United States

Predicting the stability and fitness effects of amino acid mutations in proteins is a cornerstone of biological discovery and engineering. Various experimental techniques have been developed to measure mutational effects, providing us with extensive datasets across a diverse range of proteins. By training on these data, traditional computational modeling and more recent machine learning approaches have advanced significantly in predicting mutational effects. Here, we introduce HERMES, a 3D rotationally equivariant structure-based neural network model for mutational effect and stability prediction. Pre-trained to predict amino acid propensity from its surrounding 3D structure, HERMES can be fine-tuned for mutational effects using our open-source code. We present a suite of HERMES models, pre-trained with different strategies, and fine-tuned to predict the stability effect of mutations. Benchmarking against other models shows that HERMES often outperforms or matches their performance in predicting mutational effect on stability, binding, and fitness. HERMES offers versatile tools for evaluating mutational effects and can be fine-tuned for specific predictive objectives. © 2024, CC BY.

关键词： Neural network models

Faster Optimal Coalition Structure Generation via Offline Coalition Selection and Graph-Based Search

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arXiv 2024年

作者： Taguelmimt, Redha Aknine, Samir Boukredera, Djamila Changder, Narayan Sandholm, Tuomas Univ Lyon UCBL CNRS INSA Lyon Centrale Lyon Univ Lyon 2 LIRIS UMR5205 Lyon France Laboratory of Applied Mathematics Faculty of Exact Sciences University of Bejaia Bejaia Algeria TCG Centres for Research and Education in Science and Technology Kolkata India Computer Science Department Carnegie Mellon University Pittsburgh United States Strategy Robot Inc. United States Strategic Machine Inc. United States Optimized Markets Inc. United States

Coalition formation is a key capability in multi-agent systems. An important problem in coalition formation is coalition structure generation: partitioning agents into coalitions to optimize the social welfare. This is a challenging problem that has been the subject of active research for the past three decades. In this paper, we present a novel algorithm, SMART, for the problem based on a hybridization of three innovative techniques. Two of these techniques are based on dynamic programming, where we show a powerful connection between the coalitions selected for evaluation and the performance of the algorithms. These algorithms use offline phases to optimize the choice of coalitions to evaluate. The third one uses branch-and-bound and integer partition graph search to explore the solution space. Our techniques bring a new way of approaching the problem and a new level of precision to the field. In experiments over several common value distributions, we show that the hybridization of these techniques in SMART is faster than the fastest prior algorithms (ODP-IP, BOSS) in generating optimal solutions across all the value distributions. Copyright © 2024, The Authors. All rights reserved.

关键词： Dynamic programming

Tunable phonon-driven magnon-magnon entanglement at room temperature

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arXiv 2022年

作者： Liu, Yuefei Bergman, Anders Bagrov, Andrey Delin, Anna Thonig, Danny Pereiro, Manuel Eriksson, Olle Streib, Simon Sjöqvist, Erik Azimi-Mousolou, Vahid Department of Applied Physics School of Engineering Sciences KTH Royal Institute of Technology AlbaNova University Center StockholmSE-10691 Sweden Department of Physics and Astronomy Uppsala University Box 516 UppsalaSE-751 20 Sweden Institute for Molecules and Materials Radboud University Heyendaalseweg 135 Nijmegen6525AJ Netherlands KTH Royal Institute of Technology StockholmSE-10044 Sweden School of Science and Technology Örebro University ÖrebroSE-701 82 Sweden Department of Applied Mathematics and Computer Science Faculty of Mathematics and Statistics University of Isfahan Isfahan81746-73441 Iran

We report the existence of entangled steady-states in bipartite quantum magnonic systems at elevated temperatures. We consider dissipative dynamics of two magnon modes in a bipartite antiferromagnet, subjected to interaction with a phonon mode and an external rotating magnetic field. To quantify the bipartite magnon-magnon entanglement, we use entanglement negativity and compute its dependence on temperature and magnetic field. We provide evidence that the coupling between magnon and phonon modes is necessary for the entanglement, and that, for any given phonon frequency and magnon-phonon coupling rate, there are always ranges of the magnetic field amplitudes and frequencies for which magnon-magnon entanglement persists at room temperature. Copyright © 2022, The Authors. All rights reserved.

关键词： Room temperature