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Two-dimensional charge order stabilized in clean polytype heterostructures

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arXiv 2021年

作者： Sung, Suk Hyun Schnitzer, Noah Novakov, Steve El Baggari, Ismail Luo, Xiangpeng Gim, Jiseok Vu, Nguyen M. Li, Zidong Brintlinger, Todd H. Liu, Yu Lu, Wenjian Sun, Yuping Deotare, Parag B. Sun, Kai Zhao, Liuyan Kourkoutis, Lena F. Heron, John T. Hovden, Robert Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering Cornell University IthacaNY14853 United States Kavli Institute at Cornell for Nanoscale Science IthacaNY14853 United States Department of Physics University of Michigan Ann ArborMI48109 United States Department of Physics Cornell University IthacaNY14853 United States Rowland Institute at Harvard CambridgeMA02142 United States Electrical and Computer Engineering Department University of Michigan Ann ArborMI48109 United States Materials Science and Technology Division U.S. Naval Research Laboratory WashingtonDC20375 United States Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei230031 China High Magnetic Field Laboratory Chinese Academy of Sciences Hefei230031 China Collaborative Innovation Centre of Advanced Microstructures Nanjing University Nanjing210093 China Applied Physics Program University of Michigan Ann ArborMI48109 United States School of Applied and Engineering Physics Cornell University IthacaNY14853 United States

Compelling evidence suggests distinct correlated electron behavior may exist only in clean 2D materials such as 1T-TaS2. Unfortunately, experiment and theory suggest that extrinsic disorder in free standing 2D layers disrupts correlation-driven quantum behavior. Here we demonstrate a route to realizing fragile 2D quantum states through endotaxial polytype engineering of van der Waals materials. The true isolation of 2D charge density waves (CDWs) between metallic layers stabilizes commensurate long-range order and lifts the coupling between neighboring CDW layers to restore mirror symmetries via interlayer CDW twinning. The twinned-commensurate charge density wave (tC-CDW) reported herein has a single metal–insulator phase transition at ~350 K as measured structurally and electronically. Fast in-situ transmission electron microscopy and scanned nanobeam diffraction map the formation of tC-CDWs. This work introduces endotaxial polytype engineering of van der Waals materials to access latent 2D ground states distinct from conventional 2D fabrication. © 2021, CC BY.

关键词： Charge density waves

Growth optimization and device integration of narrow-bandgap graphene nanoribbons

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arXiv 2022年

作者： Barin, Gabriela Borin Sun, Qiang Di Giovannantonio, Marco Du, Cheng-Zhuo Wang, Xiao-Ye Llinas, Juan Pablo Mutlu, Zafer Lin, Yuxuan Wilhelm, Jan Overbeck, Jan Daniels, Colin Lamparski, Michael Sahabudeen, Hafeesudeen Perrin, Mickael L. Urgel, José I. Mishra, Shantanu Kinikar, Amogh Widmer, Roland Stolz, Samuel Bommert, Max Pignedoli, Carlo Feng, Xinliang Calame, Michel Müllen, Klaus Narita, Akimitsu Meunier, Vincent Bokor, Jeffrey Fasel, Roman Ruffieux, Pascal Empa Swiss Federal Laboratories for Materials Science and Technology Dübendorf 8600 Switzerland State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Tianjin 300071 China Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA94720 United States Institute of Theoretical Physics University of Regensburg RegensburgD-93053 Germany Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute TroyNY12180 United States Center for Advancing Electronics Dresden Department of Chemistry and Food Chemistry TU Dresden Dresden01062 Germany Max Planck Institute for Polymer Research Mainz55128 Germany Department of Chemistry Johannes Gutenberg-Universität Mainz Mainz55128 Germany Organic and Carbon Nanomaterials Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa904-0495 Japan Department of Chemistry Biochemistry and Pharmaceutical Sciences University of Bern Bern3012 Switzerland

The electronic, optical and magnetic properties of graphene nanoribbons (GNRs) can be engineered by controlling their edge structure and width with atomic precision through bottom-up fabrication based on molecular precursors. This approach offers a unique platform for all-carbon electronic devices but requires careful optimization of the growth conditions to match structural requirements for successful device integration, with GNR length being the most critical parameter. In this work, we study the growth, characterization, and device integration of 5-atom wide armchair GNRs (5-AGNRs), which are expected to have an optimal band gap as active material in switching devices. 5-AGNRs are obtained via on-surface synthesis under ultrahigh vacuum conditions from Br- and I-substituted precursors. We show that the use of I-substituted precursors and the optimization of the initial precursor coverage quintupled the average 5-AGNR length. This significant length increase allowed us to integrate 5-AGNRs into devices and to realize the first field-effect transistor based on narrow bandgap AGNRs that shows switching behavior at room temperature. Our study highlights that optimized growth protocols can successfully bridge between the sub-nanometer scale, where atomic precision is needed to control the electronic properties, and the scale of tens of nanometers relevant for successful device integration of GNRs. Copyright © 2022, The Authors. All rights reserved.

关键词： X ray photoelectron spectroscopy

Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

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arXiv 2020年

作者： Bergman, Arik Duggan, Robert Sharma, Kavita Tur, Moshe Zadok, Avi Alù, Andrea Faculty of Engineering Institute for Nano-Technology and Advanced Materials Bar-Ilan University Ramat-Gan5290002 Israel Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712 United States School of Electrical Engineering Tel-Aviv University Tel-Aviv6997801 Israel Physics Program Graduate Center City University of New York New YorkNY10026 United States

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has drawn a great deal of attention in recent years. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. Among several peculiar phenomena observed at exceptional points, an especially intriguing property, with relevant practical potential, consists in the inherently enhanced sensitivity to small-scale perturbations. So far, however, these principles have been implemented at the expenses of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled distributions of optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of standard single-mode telecommunication fibre, using a setup consisting of entirely of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, which makes the process non-Hermitian and enables exquisite control over gain and loss. Singular response to small variations around the exceptional point and topological features arising around this singularity are experimentally demonstrated with large precision, enabling robustly enhanced spectral response to small-scale changes in the Brillouin frequency shift. Our findings open exciting opportunities for the exploration of non-Hermitian phenomena over a table-top setup, with straightforward extensions to higher-order Hamiltonians and applications in quantum optics, nanophotonics and sensing. Copyright © 2020, The Authors. All rights reserved.

关键词： Optical fibers

Back propagation neural network experiment on team matchmaking MOBA game 1

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Back propagation neural network experiment on team matchmaki...

1st International Conference on Information and Communications Technology, ICOIACT 2018

作者： Tanuar, Evawaty Abbas, Bahtiar Saleh Trisetyarso, Agung Kang, Chul-Ho Gaol, Ford Lumban Suparta, Wayan Computer Science Department School of Computer Science Bina Nusantara University Jakarta11480 Indonesia Computer Science Department BINUS Graduate Program - Doctor of Computer Science Bina Nusantara University Jakarta11480 Indonesia Department of Electrical Engineering Sanata Dharma University Yogyakarta55282 Indonesia

ISBN: (纸本)9781538609545

Backpropagation is one of the famous method for learning, Implementing Backpropagation techniques in games is part of AI in game. This paper aim to analyzed the best team composition in a Moba Game type in learning using neural network. Mobile Legend: Bang Bang is one of MOBA game for mobile phone. In this experiment, the 2 hidden layers back-propagation neural network algorithm is used to analyze the Mobile Legend game. 5000 training steps was done to reach the stability. This also a way of learning to find the best composition in a team played. Research in area AI and game is very wide and open, a huge opportunity to be explore in future. The objective of this research is to produce the good combination of team which can be resulted in a greater winning chance. © 2018 IEEE.

关键词： Backpropagation

Validating first-principles molecular dynamics calculations of oxide/water interfaces with x-ray reflectivity data

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Physical Review Materials 2020年第11期4卷 113805-113805页

作者： Katherine J. Harmon Kendra Letchworth-Weaver Alex P. Gaiduk Federico Giberti Francois Gygi Maria K. Y. Chan Paul Fenter Giulia Galli Applied Physics Graduate Program Northwestern University Evanston Illinois 60208 USA Center for Nanoscale Materials Argonne National Laboratory Lemont Illinois 60439 USA Pritzker School of Molecular Engineering University of Chicago Chicago Illinois 60637 USA Department of Physics and Astronomy James Madison University Harrisonburg Virginia 22807 USA Department of Computer Science University of California Davis California 95616 USA Chemical Sciences and Engineering Division Argonne National Laboratory Lemont Illinois 60439 USA Materials Science Division Argonne National Laboratory Lemont Illinois 60439 USA Department of Chemistry University of Chicago Chicago Illinois 60637 USA

Metal oxide/water interfaces play a crucial role in many electrochemical and photocatalytic processes, such as photoelectrochemical water splitting, the creation of fuel from sunlight, and electrochemical CO2 reduction. First-principles electronic structure calculations can reveal unique insights into these processes, such as the role of the alignment of the oxide electronic energy levels with those of liquid water. An essential prerequisite for the success of such calculations is the ability to predict accurate structural models of these interfaces, which in turn requires careful experimental validation. Here we report a general, quantitative validation protocol for first-principles molecular dynamics simulations of oxide/aqueous interfaces. The approach makes direct comparisons of interfacial x-ray reflectivity (XR) signals from experimental measurements and those obtained from ab initio simulations with semilocal and van der Waals functionals. The protocol is demonstrated here for the case of the Al2O3(001)/water interface, one of the simplest oxide/water interfaces. We discuss the technical requirements needed for validation, including the choice of the density functional, the simulation cell size, and the optimal choice of the thermodynamic ensemble. Our results establish a general paradigm for the validation of structural models and interactions at solid/water interfaces derived from first-principles simulations. While there is qualitative agreement between the simulated structures and the experimental best-fit structure, direct comparisons of simulated and measured XR intensities show quantitative discrepancies that derive from both bulk regions (i.e., alumina and water) as well as the interfacial region, highlighting the need for accurate density functionals to properly describe interfacial interactions. Our results show that XR data are sensitive not only to the atomic structure (i.e., the atom locations) but also to the electron-density distributions in bo

关键词： First-principles calculations Surface & interfacial phenomena Liquid-solid interfaces Electronic structure X-ray reflectivity

Tunable nanophotonics enabled by chalcogenide phase-change materials

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arXiv 2020年

作者： Abdollahramezani, Sajjad Hemmatyar, Omid Taghinejad, Hossein Krasnok, Alex Kiarashinejad, Yashar Zandehshahvar, Mohammadreza Alù, Andrea Adibi, Ali School of Electrical and Computer Engineering Georgia Institute of Technology 778 Atlantic Drive NW AtlantaGA30332-0250 United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States

Nanophotonics has garnered intensive attention due to its unique capabilities in molding the flow of light in the subwavelength regime. Metasurfaces (MSs) and photonic integrated circuits (PICs) enable the realization of mass-producible, cost-effective, and highly efficient flat optical components for imaging, sensing, and communications. In order to enable nanophotonics with multi-purpose functionalities, chalcogenide phase-change materials (PCMs) have been introduced as a promising platform for tunable and reconfigurable nanophotonic frameworks. Integration of non-volatile chalcogenide PCMs with unique properties such as drastic optical contrasts, fast switching speeds, and long-term stability grants substantial reconfiguration to the more conventional static nanophotonic platforms. In this review, we discuss state-of-the-art developments as well as emerging trends in tunable MSs and PICs using chalcogenide PCMs. We outline the unique material properties, structural transformation, electro-optic, and thermo-optic effects of well-established classes of chalcogenide PCMs. The emerging deep learning-based approaches for the optimization of reconfigurable MSs and the analysis of light-matter interactions are also discussed. The review is concluded by discussing existing challenges in the realization of adjustable nanophotonics and a perspective on the possible developments in this promising area. Copyright © 2020, The Authors. All rights reserved.

关键词： Phase change materials

Néel-type skyrmions and their current-induced motion in van der Waals ferromagnet-based heterostructures

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Physical Review B 2021年第10期103卷 104410-104410页

作者： Tae-Eon Park Licong Peng Jinghua Liang Ali Hallal Fehmi Sami Yasin Xichao Zhang Kyung Mee Song Sung Jong Kim Kwangsu Kim Markus Weigand Gisela Schütz Simone Finizio Jörg Raabe Karin Garcia Jing Xia Yan Zhou Motohiko Ezawa Xiaoxi Liu Joonyeon Chang Hyun Cheol Koo Young Duck Kim Mairbek Chshiev Albert Fert Hongxin Yang Xiuzhen Yu Seonghoon Woo Center for Spintronics Korea Institute of Science and Technology Seoul 02792 Korea RIKEN Center for Emergent Matter Science Wako 351-0198 Japan Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo 315201 China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 China Université Grenoble Alpes CEA CNRS Spintec 38000 Grenoble France School of Science and Engineering The Chinese University of Hong Kong Shenzhen Guangdong 518172 China KU-KIST Graduate School of Converging Science and Technology Korea University Seoul 02841 Korea Department of Physics University of Ulsan Ulsan 44610 Korea Helmholtz Center Berlin Albert Einstein Straβe 15 12489 Berlin Germany Max-Planck-Institut für Intelligente Systeme 70569 Stuttgart Germany Swiss Light Source Paul Scherrer Institut 5232 Villigen Switzerland DIPC and University of the Basque Country 2018 San Sebastian Spain Department of Applied Physics University of Tokyo Hongo 7-3-1 Tokyo 113-8656 Japan Department of Electrical and Computer Engineering Shinshu University Wakasato 4-17-1 Nagano 380-8553 Japan Department of Materials Science & Engineering Yonsei University Seoul 03722 Korea Department of Physics Kyung Hee University Seoul 02447 Korea Unité Mixte de Physique CNRS Thales Université Paris-Sud Université Paris-Saclay Palaiseau 91767 France IBM T.J. Watson Research Center 1101Kitchawan Road Yorktown Heights New York 10598 USA

Since the discovery of ferromagnetic two-dimensional (2D) van der Waals (vdW) crystals, significant interest on such 2D magnets has emerged, inspired by their appealing physical properties and integration with other 2D family for unique heterostructures. In known 2D magnets, spin-orbit coupling (SOC) stabilizes perpendicular magnetic anisotropy down to one or a few monolayers. Such a strong SOC could also lift the chiral degeneracy, leading to the formation of topological magnetic textures such as skyrmions through the Dzyaloshinskii-Moriya interaction (DMI). Here, we report the experimental observation of Néel-type chiral magnetic skyrmions and their lattice (SkX) formation in a vdW ferromagnet Fe3GeTe2 (FGT). We demonstrate the ability to drive an individual skyrmion by short current pulses along a vdW heterostructure, FGT/h−BN, as highly required for any skyrmion-based spintronic device. Using first principle calculations supported by experiments, we unveil the origin of DMI being the interfaces with oxides, which then allows us to engineer vdW heterostructures for desired chiral states. Our finding opens the door to topological spin textures in the 2D vdW magnet and their potential device application.

关键词： Magnetic texture Magnetism Skyrmions Spintronics

THz Generation Control in Fe/X Spintronic Multilayers by chemical bonding at epitaxial Fe/GaAs(001) interfaces

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THz Generation Control in Fe/X Spintronic Multilayers by che...

Conference on Lasers and Electro-Optics (CLEO)

作者： Roman Adam Genyu Chen Daniel E. Bürgler Derang Cao Sarah Heidtfeld Debamitra Chakraborty Jing Cheng Ivan Komissarov Hilde Hardtdegen Martin Mikulics Claus M. Schneider Roman Sobolewski Research Centre Jülich Peter Grünberg Institute (PGI-6) Jülich Germany Materials Science Graduate Program University of Rochester Rochester New York USA Laboratory for Laser Energetics University of Rochester Rochester New York USA College of Physics Center for Marine Observation and Communications Qingdao University Qingdao China Department of Electrical and Computer Engineering University of Rochester Rochester New York USA Research Centre Jülich Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons Jülich Germany Department of Physics University of California Davis Davis California USA

We report an additional degree of control of THz transients in Fe/X spintronic emitters grown on GaAs(001). We ascribe the field-independent enhancement of the THz amplitude to specific chemical bonding at the epitaxi... 详细信息

ISBN: (纸本)9781943580910

关键词： Electromagnetic radiation Free electron lasers Gallium arsenide Magnetic fields Terahertz generation Ultrafast lasers

Biphenylene monolayer as a two-dimensional nonbenzenoid carbon allotrope: A first-principles study

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arXiv 2021年

作者： Bafekry, Asadolah Faraji, M. Fadlallah, M.M. Jappor, H.R. Karbasizadeh, S. Ghergherehchi, M. Gogova, D. Department of Radiation Application Shahid Beheshti University Tehran*** Iran Micro and Nanotechnology Graduate Program TOBB University of Economics and Technology Sogutozu Caddesi No 43 Sogutozu Ankara06560 Turkey Department of Physics Faculty of Science Benha University Benha13518 Egypt Department of Physics College of Education for Pure Sciences University of Babylon Hilla Iraq Department of Physics Isfahan University of Technology Isfahan84156-83111 Iran Department of Electrical and Computer Engineering Sungkyunkwan University Suwon16419 Korea Republic of Department of Physics University of Oslo P.O. Box 1048 Blindern Oslo Norway

In a very recent accomplishment, the two-dimensional form of Biphenylene network (BPN) has been successfully fabricated [Fan et al., science, 372, 852-856 (2021)]. Motivated by this exciting experimental result on 2D layered BPN structure, herein we perform detailed density functional theory-based first-principles calculations, for the first time, in order to gain insight into the structural, electronic and optical properties of this promising nanomaterial. Our theoretical results reveal the BPN structure is constructed from three rings of tetragon, hexagon and octagon, meanwhile the electron localization function shows very strong bonds between the C atoms in the structure. The dynamical stability of BPN is verified via the phonon band dispersion calculations. The mechanical properties reveal the brittle behavior of BPN monolayer. The Young's modulus has been computed as 0.1 TPa, which is smaller than the corresponding value of graphene, while the Poisson's ratio determined to be 0.26 is larger than that of graphene. The band structure is evaluated to show the electronic features of the material;determining the BPN monolayer as metallic with a band gap of zero. The optical properties (real and imaginary parts of the dielectric function, and the absorption spectrum) uncover BPN as an insulator along the zz direction, while owning metallic properties in xx and yy directions. We anticipate that our discoveries will pave the way to the successful implementation of this new 2D allotrope of carbon in advanced nanoelectronics. © 2021, CC BY.

关键词： Monolayers