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Strong pseudospin-lattice coupling in Sr3Ir2O7: Coherent phonon anomaly and negative thermal expansion

Physical Review B 2019年第9期99卷 094307-094307页

作者： L. L. Hu M. Yang Y. L. Wu Q. Wu H. Zhao F. Sun W. Wang Rui He S. L. He H. Zhang R. J. Huang L. F. Li Y. G. Shi Jimin Zhao Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100049 China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190 China Department of Electrical and Computer Engineering Texas Tech University Lubbock Texas 79409 USA Ningbo Institute of Material Technology & Engineering Chinese Academy of Sciences Ningbo 315201 China College of Physical Science and Technology Sichuan University Chengdu 610065 China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China

The similarities to cuprates make iridates an interesting potential platform for investigating superconductivity. Equally attractive are their puzzling complex intrinsic interactions. Here, we report an ultrafast optical spectroscopy investigation of a coherent phonon mode in Sr3Ir2O7, a bilayer Ruddlesden-Popper perovskite iridate. An anomaly in the A1g optical phonon (ν=4.4THz) is unambiguously observed below the Néel temperature (TN), which we attribute to pseudospin-lattice coupling (PLC). Significantly, we find that PLC is the dominant interaction at low temperature, and we directly measure the PLC coefficient to be λ=150±20cm−1, which is two orders of magnitude higher than that in manganites (<2.4cm−1) and comparable to that in CuO (50cm−1, the strongest PLC or spin-lattice coupling (SLC) previously known). Moreover, we find that the strong PLC induces an anisotropic negative thermal expansion. Our findings highlight the key role of PLC in iridates and uncovers another intriguing similarity to cuprates.

关键词： Lattice dynamics Phonons Ultrafast phenomena Strongly correlated systems

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Gate-tunable memristors from monolayer MoS2

arXiv

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arXiv 2018年

作者： Sangwan, Vinod K. Lee, Hong-Sub Hersam, Mark C. Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

We report here gate-tunable memristors based on monolayer MoS2grown by chemical vapor deposition (CVD). These memristors are fabricated in a field-effect geometry with the channel consisting of polycrystalline MoS2films with grain sizes of 3-5 μm. The device characteristics show switching ratios up to ∼500, with the resistance in individual states being continuously gate-tunable by over three orders of magnitude. The resistive switching results from dynamically varying threshold voltage and Schottky barrier heights, whose underlying physical mechanism appears to be vacancy migration and/or charge trapping. Top-gated devices achieve reversible tuning of threshold voltage, with potential utility in non-volatile memory or neuromorphic architectures. Copyright © 2018, The Authors. All rights reserved.

关键词： Molybdenum compounds

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Multi-terminal memtransistors from polycrystalline monolayer MoS2

arXiv

引用

arXiv 2018年

作者： Sangwan, Vinod K. Lee, Hong-Sub Bergeron, Hadallia Balla, Itamar Beck, Megan E. Chen, Kan-Sheng Hersam, Mark C. Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

In the last decade, a 2-terminal passive circuit element called a memristor has been developed for non-volatile resistive random access memory and has more recently shown promise for neuromorphic computing.1, 2, 3, 4, 5, 6 Compared to flash memory, memristors have higher endurance, multi-bit data storage, and faster read/write times.4, 7, 8 However, although 2-terminal memristors have demonstrated basic neural functions, synapses in the human brain outnumber neurons by more than a factor of 1000, which implies that multi-terminal memristors are needed to perform complex functions such as heterosynaptic plasticity.3, 9, 10, 11, 12, 13 Previous attempts to move beyond 2-terminal memristors include the 3-terminal Widrow-Hoff memistor14 and field-effect transistors with nanoionic gates15 or floating gates,16 albeit without memristive switching in the transistor.17 Here, we report the scalable experimental realization of a multi-terminal hybrid memristor and transistor (i.e., memtransistor) using polycrystalline monolayer MoS2. Two-dimensional (2D) MoS2 memtransistors show gate tunability in individual states by 4 orders of magnitude in addition to large switching ratios with high cycling endurance and long-term retention of states. In addition to conventional neural learning behavior of long-term potentiation/depression, 6-terminal MoS2 memtransistors possess gate-tunable heterosynaptic functionality that is not achievable using 2-terminal memristors. For example, the conductance between a pair of two floating electrodes (pre-synaptic and post-synaptic neurons) is varied by ~10× by applying voltage pulses to modulatory terminals. In situ scanning probe microscopy, cryogenic charge transport measurements, and device modeling reveal that bias-induced MoS2 defect motion drives resistive switching by dynamically varying Schottky barrier heights. Overall, the seamless integration of a memristor and transistor into one multi-terminal device has the potential to enable complex

关键词： Molybdenum compounds

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Observation of Narrow-Band Terahertz Gain in Two-Dimensional Magnetoexcitons

Observation of Narrow-Band Terahertz Gain in Two-Dimensional...

引用

2019 Conference on Lasers and Electro-Optics, CLEO 2019

作者： Li, Xinwei Yoshioka, Katsumasa Zhang, Qi Katsutani, Fumiya Gao, Weilu Marquez, Nicolas Timothy Noe, G. Watson, John D. Manfra, Michael J. Katayama, Ikufumi Takeda, Jun Kono, Junichiro Deparment of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Physics Graduate School of Engineering Yokohama National University Yokohama240-8501 Japan Argonne National Laboratories LemontIL60439 United States Deparment of Physics and Astronomy Rice University HoustonTX77005 United States Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Deparment of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

We have performed time- and polarization-resolved optical-pump-terahertz-probe magnetospectroscopy measurements on a GaAs quantum well and observed narrow-band, polarization-selective THz gain, whose center frequency ... 详细信息

ISBN: (纸本)9781943580576

关键词： Magnetic fields Conductivity Probes Gallium arsenide Excitons Magnetic field measurement Time-frequency analysis"

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Electronic transport in two-dimensional materials

arXiv

引用

arXiv 2018年

作者： Sangwan, Vinod K. Hersam, Mark C. Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

Two-dimensional (2D) materials have captured the attention of the scientific community due to the wide range of unique properties at nanometer-scale thicknesses. While significant exploratory research in 2D materials has been achieved, the understanding of 2D electronic transport and carrier dynamics remains in a nascent stage. Furthermore, since prior review articles have provided general overviews of 2D materials or specifically focused on charge transport in graphene, here we instead highlight charge transport mechanisms in post-graphene 2D materials with particular emphasis on transition metal dichalcogenides and black phosphorus. For these systems, we delineate the intricacies of electronic transport including bandstructure control with thickness and external fields, valley polarization, scattering mechanisms, electrical contacts, and doping. In addition, electronic interactions between 2D materials are considered in the form of van der Waals heterojunctions and composite films. This review concludes with a perspective on the most promising future directions in this fast-evolving field. Copyright © 2018, The Authors. All rights reserved.

关键词： Van der Waals forces

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L10-FePd synthetic antiferromagnet through a face-centered-cubic Ruthenium spacer utilized for perpendicular magnetic tunnel junctions

arXiv

引用

arXiv 2018年

作者： Zhang, De-Lin Sun, Congli Lv, Yang Schliep, Karl B. Zhao, Zhengyang Chen, Jun-Yang Voyles, Paul M. Wang, Jian-Ping Department of Electrical and Computer Engineering University of Minnesota 200 Union Street SE MinneapolisMN55455 United States Department of Chemical Engineering and Materials Science University of Minnesota 421 Washington Avenue SE MinneapolisMN55455 United States Department of Materials Science and Engineering University of Wisconsin-Madison MadisonWI53706 United States

Magnetic materials that possess large bulk perpendicular magnetic anisotropy (PMA) are essential for the development of magnetic tunnel junctions (MTJs) used in future spintronic memory and logic devices. The addition of an antiferromagnetic layer to these MTJs was recently predicted to facilitate ultrafast magnetization switching. Here, we report a demonstration of bulk perpendicular synthetic antiferromagnetic (p-SAF) structure comprised of an (001) textured FePd/Ru/FePd trilayer with a face-centered-cubic (fcc) phase Ruthenium spacer. The L10-FePd p-SAF structure shows a large bulk PMA (Ku~10.2 Merg/cm3) and strong antiferromagnetic coupling (-Jiec~2.60 erg/cm2). Full perpendicular magnetic tunnel junctions (p-MTJs) with L10-FePd p-SAF layer were then fabricated. Tunneling magnetoresistance ratios of up to ~25% (~60%) are observed at room temperature (5 K) after post-annealing at 350 oC. Exhibiting high thermal stabilities and large Ku, the bulk p-MTJs with a L10-FePd p-SAF layer could pave a way for next-generation ultra-high-density and ultralow-energy spintronic applications. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetic devices

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Inverse-designed photonic circuits for fully passive, bias-free Kerr-based nonreciprocal transmission and routing

arXiv

引用

arXiv 2019年

作者： Yang, Ki Youl Skarda, Jinhie Cotrufo, Michele Dutt, Avik Ahn, Geun Ho Vercruysse, Dries Fan, Shanhui Alù, Andrea Vucković, Jelena E. L. Ginzton Laboratory Stanford University StanfordCA94305 United States 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 New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States Department of Electrical Engineering City University of New York New YorkNY10031 United States

Nonreciprocal devices such as isolators and circulators are key enabling technologies for communication systems, both at microwave and optical frequencies. While nonreciprocal devices based on magnetic effects are available for free-space and fibre-optic communication systems, their on-chip integration has been challenging, primarily due to the concomitant high insertion loss, weak magneto-optical effects, and material incompatibility. We show that Kerr nonlinear resonators can be used to achieve all-passive, low-loss, bias-free, broadband nonreciprocal transmission and routing for applications in photonic systems such as chip-scale LIDAR. A multi-port nonlinear Fano resonator is used as an on-chip, all-optical router for frequency comb based distance measurement. Since time-reversal symmetry imposes stringent limitations on the operating power range and transmission of a single nonlinear resonator, we implement a cascaded Fano-Lorentzian resonator system that overcomes these limitations and significantly improves the insertion loss, bandwidth and non-reciprocal power range of current state-of-the-art devices. This work provides a platform-independent design for nonreciprocal transmission and routing that are ideally suited for photonic integration. Copyright © 2019, The Authors. All rights reserved.

关键词： Insertion losses

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Development of an optical fiber-based sensor for grasping and axial force sensing

Development of an optical fiber-based sensor for grasping an...

引用

2017 IEEE International Conference on Robotics and Automation, ICRA 2017

作者： Zarrin, Pouya Soltani Escoto, Abelardo Xu, Ran Patel, Rajni V. Naish, Michael D. Trejos, Ana Luisa CSTAR Lawson Health Research Institute Biomedical Engineering Program at Western LondonON Canada CSTAR United States CTAR Department of Electrical and Computer Engineering Western United States CSTAR Department of Electrical and Computer Engineering United States CSTAR Department of Mechanical and Materials Engineering Western United States

ISBN: (纸本)9781509046331

In spite of the remarkable benefits that minimally invasive surgery provides for patients, the absence of force feedback is still a significant disadvantage. Several studies have been performed to address this issue;however, an accurate sterilizable force sensing technology for measuring axial and grasping forces is still missing. In this work, an innovative partial grasper has been designed and developed for a laparoscopic needle driver that can measure axial and grasping force information at the grasper tip. Fiber Bragg Grating sensors are used in this work because of their sterilizability and high sensitivity. Accuracies of 0.19 N and 0.26 N were achieved for the grasping and axial sensors respectively. © 2017 IEEE.

关键词： Fiber Bragg gratings

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A Novel OCT Design for Cultural Heritage Applications

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Microscopy and Microanalysis 2018年第S1期24卷 2142-2143页

作者： Danielle Duggins Fengqiang Li Maurice Aalders Oliver Cossairt Aggelos Katsaggelos Marc Walton Northwestern University Department of Materials Science & Engineering Evanston IL USA Northwestern University Department of Electrical Engineering and Computer Science Evanston IL USA University of Amsterdam Department of Biomedical Engineering and Physics Academic Medical Center Amsterdam Netherlands Northwestern University/Art Institute of Chicago Center for Scientific Studies of the Arts (NU- ACCESS) Evanston IL Chicago USA

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Federated Learning Enables Big Data for Rare Cancer Boundary Detection

arXiv

引用

arXiv 2022年

作者： Pati, Sarthak Baid, Ujjwal Edwards, Brandon Sheller, Micah Wang, Shih-Han Reina, G. Anthony Foley, Patrick Gruzdev, Alexey Karkada, Deepthi Davatzikos, Christos Sako, Chiharu Ghodasara, Satyam Bilello, Michel Mohan, Suyash Vollmuth, Philipp Brugnara, Gianluca Preetha, Chandrakanth J. Sahm, Felix Maier-Hein, Klaus Zenk, Maximilian Bendszus, Martin Wick, Wolfgang Calabrese, Evan Rudie, Jeffrey Villanueva-Meyer, Javier Cha, Soonmee Ingalhalikar, Madhura Jadhav, Manali Pandey, Umang Saini, Jitender Garrett, John Larson, Matthew Jeraj, Robert Currie, Stuart Frood, Russell Fatania, Kavi Huang, Raymond Y. Chang, Ken Balana, Carmen Capellades, Jaume Puig, Josep Trenkler, Johannes Pichler, Josef Necker, Georg Haunschmidt, Andreas Meckel, Stephan Shukla, Gaurav Liem, Spencer Alexander, Gregory S. Lombardo, Joseph Palmer, Joshua D. Flanders, Adam E. Dicker, Adam P. Sair, Haris I. Jones, Craig K. Venkataraman, Archana Jiang, Meirui So, Tiffany Y. Chen, Cheng Heng, Pheng Ann Dou, Qi Kozubek, Michal Lux, Filip Michálek, Jan Matula, Petr Keřkovský, Miloš Kopřivová, Tereza Dostál, Marek Vybíhal, Václav Vogelbaum, Michael A. Mitchell, J. Ross Farinhas, Joaquim Maldjian, Joseph A. Yogananda, Chandan Ganesh Bangalore Pinho, Marco C. Reddy, Divya Holcomb, James Wagner, Benjamin C. Ellingson, Benjamin M. Cloughesy, Timothy F. Raymond, Catalina Oughourlian, Talia Hagiwara, Akifumi Wang, Chencai To, Minh-Son Bhardwaj, Sargam Chong, Chee Agzarian, Marc Falcão, Alexandre Xavier Martins, Samuel B. Teixeira, Bernardo C.A. Sprenger, Flávia Menotti, David Lucio, Diego R. LaMontagne, Pamela Marcus, Daniel Wiestler, Benedikt Kofler, Florian Ezhov, Ivan Metz, Marie Jain, Rajan Lee, Matthew Lui, Yvonne W. McKinley, Richard Slotboom, Johannes Radojewski, Piotr Meier, Raphael Wiest, Roland Derrick, Murcia Fu, Eric Haas, Rourke Thompson, John Ormond, David Ryan Badve, Chaitra Sloan, Andrew E. Vadmal, Vachan Waite, Kristin Colen, Rivka R. Pei, Linmin Ak, Murat Srinivasan, Ashok Bapuraj, J. Rajiv Rao, Arvind Wang, Nicholas Yoshiaki, Ota Moritani, Tos University of Pennsylvania PhiladelphiaPA United States Department of Radiology Perelman School of Medicine University of Pennsylvania PhiladelphiaPA United States Department of Pathology Laboratory Medicine Perelman School of Medicine University of Pennsylvania PhiladelphiaPA United States Department of Informatics Technical University of Munich Bavaria Munich Germany Intel Corporation Santa ClaraCA United States Department of Quantitative Biomedicine University of Zurich Zurich Switzerland Department of Neuroradiology Heidelberg University Hospital Heidelberg Germany Heidelberg Germany Department of Neuropathology Heidelberg University Hospital Heidelberg Germany Division of Medical Image Computing German Cancer Research Center Heidelberg Germany Neurology Clinic Heidelberg University Hospital Heidelberg Germany Department of Radiology & Biomedical Imaging University of California San Francisco San FranciscoCA United States Symbiosis Center for Medical Image Analysis Symbiosis International University Maharashtra Pune India Department of Neuroimaging and Interventional Radiology National Institute of Mental Health and Neurosciences Karnataka Bangalore India Department of Radiology School of Medicine and Public Health University of Wisconsin MadisonWI United States Department of Medical Physics School of Medicine and Public Health University of Wisconsin MadisonWI United States Department of Neuroradiology Clinical Neuroscience Center University Hospital Zurich University of Zurich Zurich Switzerland Leeds Teaching Hospitals Trust Department of Radiology Leeds United Kingdom Department of Radiology Brigham and Women's Hospital Harvard Medical School BostonMA United States Athinoula A. Martinos Center for Biomedical Imaging Massachusetts General Hospital CharlestownMA United States Catalan Institute of Oncology Badalona Spain Consorci MAR Parc de Salut de Barcelona Catalonia Spain Josep Trueta University Hospital Girona Spain

Although machine learning (ML) has shown promise in numerous domains, there are concerns about generalizability to out-of-sample data. This is currently addressed by centrally sharing ample, and importantly diverse, data from multiple sites. However, such centralization is challenging to scale (or even not feasible) due to various limitations. Federated ML (FL) provides an alternative to train accurate and generalizable ML models, by only sharing numerical model updates. Here we present findings from the largest FL study to-date, involving data from 71 healthcare institutions across 6 continents, to generate an automatic tumor boundary detector for the rare disease of glioblastoma, utilizing the largest dataset of such patients ever used in the literature (25,256 MRI scans from 6,314 patients). We demonstrate a 33% improvement over a publicly trained model to delineate the surgically targetable tumor, and 23% improvement over the tumor's entire extent. We anticipate our study to: 1) enable more studies in healthcare informed by large and diverse data, ensuring meaningful results for rare diseases and underrepresented populations, 2) facilitate further quantitative analyses for glioblastoma via performance optimization of our consensus model for eventual public release, and 3) demonstrate the effectiveness of FL at such scale and task complexity as a paradigm shift for multi-site collaborations, alleviating the need for data sharing. © 2022, CC BY.

关键词： Tumors

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