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Valley-polarized Exitonic Mott Insulator in WS2/WSe2 Moiré Superlattice

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arXiv 2023年

作者： Lian, Zhen Meng, Yuze Ma, Lei Maity, Indrajit Yan, Li Wu, Qiran Huang, Xiong Chen, Dongxue Chen, Xiaotong Chen, Xinyue Blei, Mark Taniguchi, Takashi Watanabe, Kenji Tongay, Sefaattin Lischner, Johannes Cui, Yong-Tao Shi, Su-Fei Department of Chemical and Biological Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Departments of Materials The Thomas Young Centre for Theory and Simulation of Materials Imperial College London United Kingdom Department of Physics and Astronomy University of California RiversideCA92521 United States Department of Materials Science and Engineering University of California RiversideCA92521 United States Materials Science and Engineering Program School for Engineering of Matter Transport and Energy Arizona State University TempeAZ85287 United States International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Electrical Computer & Systems Engineering Rensselaer Polytechnic Institute TroyNY12180 United States

Strongly enhanced electron-electron interaction in semiconducting moiré superlattices formed by transition metal dichalcogenides (TMDCs) heterobilayers has led to a plethora of intriguing fermionic correlated states1–7. Meanwhile, interlayer excitons in a type-II aligned TMDC heterobilayer moiré superlattice, with electrons and holes separated in different layers8,9, inherit this enhanced interaction and strongly interact with each other, promising for realizing tunable correlated bosonic quasiparticles10,11 with valley degree of freedom. We employ photoluminescence spectroscopy to investigate the strong repulsion between interlayer excitons and correlated electrons in a WS2/WSe2 moiré superlattice and combine with theoretical calculations to reveal the spatial extent of interlayer excitons and the band hierarchy of correlated states. We further find that an excitonic Mott insulator state emerges when one interlayer exciton occupies one moiré cell, evidenced by emerging photoluminescence peaks under increased optical excitation power. Double occupancy of excitons in one unit cell requires overcoming the energy cost of exciton-exciton repulsion of about 30-40 meV, depending on the stacking configuration of the WS2/WSe2 heterobilayer. Further, the valley polarization of the excitonic Mott insulator state is enhanced by nearly one order of magnitude. Our study demonstrates the WS2/WSe2 moiré superlattice as a promising platform for engineering and exploring new correlated states of fermion, bosons, and a mixture of both12 © 2023, CC BY.

关键词： Excitons

Metallic vs. Semiconducting properties of quasi-one-dimensional tantalum selenide van der Waals nanoribbons

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arXiv 2021年

作者： Kargar, Fariborz Krayev, Andrey Wurch, Michelle Ghafouri, Yassamin Debnath, Topojit Wickramaratne, Darshana Salguero, Tina T. Lake, Roger Bartels, Ludwig Balandin, Alexander A. Center Department of Electrical and Computer Engineering University of California RiversideCA92521 United States HORIBA Scientific NovatoCA94949 United States Department of Chemistry and Material Science and Engineering Program University of California RiversideCA92521 United States Department of Chemistry University of Georgia AthensGA30602 United States Laboratory for Terahertz and Terascale Electronics Department of Electrical and Computer Engineering University of California RiversideCA92521 United States Center for Computational Materials Science U.S. Naval Research Laboratory WashingtonDC20375 United States

We conducted a tip-enhanced Raman scattering spectroscopy (TERS) and photoluminescence (PL) study of quasi-1D TaSe3-δ nanoribbons exfoliated onto gold substrates. At a selenium deficiency of δ~0.25 (Se/Ta=2.75,), the nanoribbons exhibit a strong, broad PL peak centered around ~920 nm (1.35 eV), suggesting their semiconducting behavior. Such nanoribbons revealed a strong TERS response under 785-nm laser excitation, allowing for their nanoscale spectroscopic imaging. Nanoribbons with a smaller selenium deficiency (Se/Ta=2.85, δ~0.15) did not show any PL or TERS response. The confocal Raman spectra of these samples agree with the previously-reported spectra of metallic TaSe3. The differences in the optical response of the nanoribbons examined in this study suggest that even small variations in Se content can induce changes in electronic structure, causing samples to exhibit either metallic or semiconducting character. The temperature-dependent electrical measurements of devices fabricated with both types of materials corroborate these observations. The density-functional-theory calculations revealed that incorporation of an oxygen atom in a Se vacancy can result in band gap opening and thus enable the transition from a metal to a semiconductor. However, the predicted bandgap is substantially smaller than that derived from PL data. These results indicate that the properties of van der Waals materials can vary significantly depending on stoichiometry, defect types and concentration, and possibly environmental and substrate effects. In view of this finding, local probing of nanoribbon properties with TERS becomes essential to understanding such low-dimensional systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Van der Waals forces

Implementation of Generate and Test Algorithm for Junior High School Zoning System in Malang 4

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Implementation of Generate and Test Algorithm for Junior Hig...

4th International Conference on Vocational Education and Training, ICOVET 2020

作者： Ratnasar, Novia Agustin Mawarni, Inggar Tri Nur Handayani, Anik Wibawa, Aji Prasetya Hammad, Jehad A. H Wibowotomo, Budi Sugandi, MacHmud Universitas Negeri Malang Vocational Education Program Department Indonesia Universitas Negeri Malang Electrical Engineering Dept Indonesia Al-Quds Open University Faculty of Technology and Applied Sciences Department of Computer Information Systems Palestine Universitas Negeri Malang Industrial Technology Department Malang65145 Indonesia Universitas Negeri Malang Mechanical ENgineering Department Malang65145 Indonesia

ISBN: (纸本)9781728181318

Admission of new students in 2019 through zoning still faces many obstacles, one of which is the readiness of the application to determine the distance of a student's house from the nearest recommended school. The purpose of this study is to provide better recommendations regarding the shortest and most accurate distance in the zoning system for admission of junior high school students in Malang by using the Generate and Test algorithm without having to do it manually or using other map applications. The results of this study indicate that the distance value obtained from the haversine formula corresponds to the original distance measured through a zoning application that applies the Generate and Test algorithm to measure the closest distance from the student's location. The recommended distance is given through a process of repetition and comparison of nodes. By using the generate and test algorithm for the search process the shortest distance from the user to the destination school has an average time of 6.2MB, the level of accuracy is the same as the Haversine calculation. © 2020 IEEE.

关键词： Students

Synergetic Effect of Nonthermal Plasma and Supported Cobalt Catalyst in Plasma-Enhanced Co2 Hydrogenation

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SSRN

SSRN 2022年

作者： Song, Chunshan Wang, Jiajie Wang, Xiaoxing AlQahtani, Mohammad S. Knecht, Sean D. Bilén, Sven G. Chu, Wei Department of Chemical Engineering Sichuan University Chengdu610065 China Clean Fuels & Catalysis Program EMS Energy Institute Department of Energy and Mineral Engineering The Pennsylvania State University University ParkPA16802 United States Department of Chemical Engineering The Pennsylvania State University University ParkPA16802 United States School of Engineering Design Technology and Professional Programs The Pennsylvania State University University ParkPA16802 United States School of Electrical Engineering and Computer Science The Pennsylvania State University University ParkPA16802 United States Department of Chemistry Faculty of Science The Chinese University of Hong Kong NT Hong Kong Shatin China

Nonthermal plasma can provide an alternative to CO 2 utilization under mild conditions. Understanding the effect of plasma on catalysis is highly desired. Herein, a comparative study was performed on CO 2 hydrogenation under thermal catalytic and plasma catalytic conditions using an alumina-supported cobalt catalyst. Significant plasma-catalyst synergy was attained at the low-temperature range between 423 K and 498 K where the CO 2 conversion increased up to approximately 3.6 times of the sum of that using plasma or catalyst individually. The plasma-catalytic reaction showed a significantly lower activation energy (~40 kJ/mol), which is only half of that in the thermal catalytic reaction (~80 kJ/mol). Kinetic analysis and DRIFTS results indicate that CO 2 activation is promoted by plasma with the assistance of active H species from gas phase. Furthermore, the total H 2 adsorption capacity and the coverage of unrecyclable adsorbed H species on the metal surface were decreased under plasma. The promotion effect is very likely due to a new reaction pathway introduced by plasma. In addition, the structure and morphology changes of spent catalysts after thermal or plasma reaction were not significant, suggesting they contribute little to the synergetic effect observed under the conditions. © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

High-temperature electromagnetic and thermal characteristics of graphene composites

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arXiv 2020年

作者： Barani, Zahra Kargar, Fariborz Mohammadzadeh, Amirmahdi Naghibi, Sahar Lo, Carissa Rivera, Brandon Balandin, Alexander A. Center Materials Science and Engineering Program University of California RiversideCA92521 United States Department of Electrical and Computer Engineering Bourns College of Engineering University of California RiversideCA92521 United States

We describe a method for scalable synthesis of epoxy composites with graphene and few-layer graphene fillers, and report on the electromagnetic interference (EMI) shielding and thermal properties of such composites at elevated temperatures. The tested materials reveal excellent total EMI shielding of SET~ 65 dB (~105 dB) at a thickness of 1 mm (~2 mm) in the X-band frequency range of f = 8.2 GHz − 12.4 GHz. The room-temperature cross-plane thermal conductivity of the composite with ~19.5 vol% of fillers was determined to be K ≈ 11.2 ± 0.9 Wm−1K−1, which is a factor of ×41 larger than that of the pristine epoxy. Interestingly, the EMI shielding efficiency improves further as the temperature increases to 520 K while the thermal conductivity remains approximately constant. The excellent EMI shielding and heat conduction characteristics of such multifunctional graphene composites at elevated temperatures are promising for packaging applications of microwave components where EMI shielding and thermal management are important design considerations. Copyright © 2020, The Authors. All rights reserved.

关键词： Graphene

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

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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

Reconstruction of Fragmented Trajectories of Collective Motion using Hadamard Deep Autoencoders

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arXiv 2021年

作者： Gajamannage, Kelum Park, Yonggi Paffenroth, Randy Jayasumana, Anura P. Department of Mathematics and Statistics Texas A&M University–Corpus Christi Corpus ChristiTX78412 United States Department of Mathematical Sciences Department of Computer Science Data Science Program Worcester Polytechnic Institute WorcesterMA01609 United States Department of Electrical and Computer Engineering Colorado State University Fort CollinsCO80525 United States

Learning dynamics of collectively moving agents such as fish or humans is an active field in research. Due to natural phenomena such as occlusion and change of illumination, the multi-object methods tracking such dynamics might lose track of the agents where that might result fragmentation in the constructed trajectories. Here, we present an extended deep autoencoder (DA) that we train only on fully observed segments of the trajectories by defining its loss function as the Hadamard product of a binary indicator matrix with the absolute difference between the outputs and the labels. The trajectories of the agents practicing collective motion is low-rank due to mutual interactions and dependencies between the agents that we utilize as the underlying pattern that our Hadamard deep autoencoder (HDA) codes during its training. The performance of our HDA is compared with that of a low-rank matrix completion scheme in the context of fragmented trajectory reconstruction. © 2021, CC BY.

关键词： Learning systems

3D-Printed electrochemical sensor-integrated transwell systems

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Microsystems & Nanoengineering 2020年第1期6卷 357-368页

作者： Pradeep Ramiah Rajasekaran Ashley Augustiny Chapin David N.Quan Jens Herberholz William E.Bentley Reza Ghodssi Institute for Systems Research University of MarylandCollege ParkMDUSA Fischell Department of Bioengineering University of MarylandCollege ParkMDUSA Department of Psychology and Neuroscience and Cognitive Science Program University of MarylandCollege ParkMDUSA Institute for Bioscience and Biotechnology Research University of MarylandCollege ParkMDUSA Robert E.Fischell Institute for Biomedical Devices University of MarylandCollege ParkMDUSA Department of Electrical and Computer Engineering University of MarylandCollege ParkMDUSA

This work presents a 3D-printed,modular,electrochemical sensor-integrated transwell system for monitoring cellular and molecular events in situ without sample extraction or microfluidics-assisted downstream *** additive manufacturing techniques such as 3D printing,shadow masking,and molding are used to fabricate this modular system,which is autoclavable,biocompatible,and designed to operate following standard operating protocols(SOPs)of cellular *** to the platform is a flexible porous membrane,which is used as a cell culture substrate similarly to a commercial transwell *** electrochemical sensors fabricated on the membrane allow direct access to cells and their products.A pair of gold electrodes on the top side of the membrane measures impedance over the course of cell attachment and growth,characterized by an exponential decrease(~160%at 10Hz)due to an increase in the double layer capacitance from secreted extracellular matrix(ECM)*** voltammetry(CV)sensor electrodes,fabricated on the bottom side of the membrane,enable sensing of molecular release at the site of cell culture without the need for downstream ***-time detection of ferrocene dimethanol injection across the membrane showed a three order-of-magnitude higher signal at the membrane than in the bulk media after reaching *** modular sensor-integrated transwell system allows unprecedented direct,real-time,and noninvasive access to physical and biochemical information,which cannot be obtained in a conventional transwell system.

关键词： transwell electrochemical culture

Nanoplasmonic microbubble and nanoplasmonic sensing – Two birds in one stone

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Nanoplasmonic microbubble and nanoplasmonic sensing – Two b...

Optical Sensors, Sensors 2020 - Part of Optical Sensors and Sensing Congress 2020

作者： Ohannesian, Nareg Misbah, Ibrahim Shih, Wei-Chuan Department of Electrical and Computer Engineering University of Houston 4800 Calhoun Rd HoustonTX77004 United States Department of Biomedical Engineering University of Houston 4800 Calhoun Rd HoustonTX77004 United States Program of Materials Science and Engineering University of Houston 4800 Calhoun Rd HoustonTX77004 United States Department of Chemistry University of Houston 4800 Calhoun Rd HoustonTX77004 United States

ISBN: (纸本)9781557528209

We present low power operated nanoplasmonic microbubble generation using near infrared light for particle concentrating on high-density arrayed nanoporous gold disks. Utilizing a spatial light modulator provides precise control of size and location of multiple microbubbles. After concentrating, various nanoplasmonic sensing techniques can be directly performed. © OSA 2020.

关键词： Infrared devices