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Advanced Sustainable Systems 2021年第7期5卷

作者： Shira Gavriely Wisnu Hadibrata Roman Nudelman Koray Aydin Shachar Richter Department of Material Science and Engineering and University Center for Nanoscience and Nanotechnology The Iby and Aladar Fleischman Faculty of Engineering Tel Aviv University Tel-Aviv 6997801 Israel Department of Electrical and Computer Engineering Northwestern University Evanston IL 60208 USA

Terahertz Emission from Anomalous Hall Effect in a Single-Layer Ferromagnet

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Physical Review Applied 2019年第5期12卷 054027-054027页

作者： Qi Zhang Ziyan Luo Hong Li Yumeng Yang Xinhai Zhang Yihong Wu Department of Electrical and Computer Engineering National University of Singapore 4 Engineering Drive 3 Singapore 117583 Singapore Department of Electrical and Electronic Engineering Southern University of Science and Technology Xueyuan Rd 1088 Shenzhen 518055 China Institute of Applied Physics and Material Engineering University of Macau Avenida da Universidade Macau 999078 China

We report on terahertz (THz) emission from a single-layer ferromagnet, which involves the generation of backflow nonthermal charge current from the ferromagnet/dielectric interface by femtosecond laser excitation and subsequent conversion of the charge current to a transverse transient charge current via the anomalous Hall effect, thereby generating THz radiation. The THz emission can be either enhanced or suppressed or the polarity can be reversed by introducing a magnetization gradient in the thickness direction of the ferromagnet. Unlike spintronic THz emitters reported previously, it does not require an additional nonmagnetic layer or Rashba interface.

关键词： Anomalous Hall effect Photonics Spintronics Surface & interfacial phenomena Ferromagnets Optical sources & detectors Ultrathin films Terahertz techniques

Enhanced metal-insulator transition in freestanding VO2 down to 5 nm thickness

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arXiv 2021年

作者： Han, Kun Wu, Liang Cao, Yu Wang, Hanyu Ye, Chen Huang, Ke Motapothula, M. Xing, Hongna Li, Xinghua Qi, Dong-Chen Li, Xiao Renshaw Wang, X. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore Key Laboratory of Structure Functional Regulation of Hybrid Materials Ministry of Education Institutes of Physical Science and Information Technology Anhui University Hefei230601 China School of Material Science and Engineering Kunming University of Science and Technology Yunnan Kunming650093 China Department of Electrical and Computer Engineering National University of Singapore 4 Engineering Drive 3 Singapore117583 Singapore School of Physics and Technology Nanjing Normal University Nanjing210023 China Department of Physics and Astronomy Uppsala University Box 516 UppsalaSE-75120 Sweden Department of Physics SRM University AP Andhra Pradesh Amaravati522-502 India School of Physics Northwest University Xi'an710069 China Centre for Materials Science School of Chemistry and Physics Queensland University of Technology BrisbaneQLD4001 Australia School of Electrical and Electronic Engineering Nanyang Technological University 50 Nanyang Ave 639798 Singapore

Ultrathin freestanding membranes with a pronounced metal-insulator transition (MIT) provides huge potential in future flexible electronic applications as well as a unique aspect of the study of lattice-electron interplay. However, the reduction of the thickness to an ultrathin region (a few nm) is typically detrimental to the MIT in epitaxial films, and even catastrophic for their freestanding form. Here, we report an enhanced MIT in VO2-based freestanding membranes, with a lateral size up to millimetres and VO2 thickness down to 5 nm. The VO2-membranes were detached by dissolving a Sr3Al2O6 sacrificial layer between the VO2 thin film and c-Al2O3(0001) substrate, allowing a transfer onto arbitrary surfaces. Furthermore, the MIT in the VO2-membrane was greatly enhanced by inserting an intermediate Al2O3 buffer layer. In comparison to the best available ultrathin VO2-membranes, the enhancement of MIT is over 400% at 5 nm VO2 thickness and more than one order of magnitude for VO2 above 10 nm. Our study widens the spectrum of functionality in ultrathin and large-scale membranes, and enables the potential integration of MIT into flexible electronics and photonics. Copyright © 2021, The Authors. All rights reserved.

关键词： Vanadium dioxide

Portable magnetic particle spectrometer (MPS) for future rapid and wash-free bioassays

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arXiv 2020年

作者： Wu, Kai Chugh, Vinit Kumar Di Girolamo, Arturo Liu, Jinming Saha, Renata Su, Diqing Krishna, Venkatramana D. Nair, Abilash Davies, Will Wang, Andrew Yongqiang Cheeran, Maxim C.-J. Wang, Jian-Ping Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Department of Chemical Engineering and Material Science University of Minnesota MinneapolisMN55455 United States Department of Veterinary Population Medicine University of Minnesota St. PaulMN55108 United States Department of Computer Science University of Minnesota MinneapolisMN55455 United States Ocean Nano Tech LLC San DiegoCA92126 United States

Nowadays, there is an increasing demand for more accessible routine diagnostics for patients with respect to high accuracy, ease of use, and low cost. However, the quantitative and high accuracy bioassays in large hospitals and laboratories usually require trained technicians and equipment that is both bulky and expensive. In addition, the multi-step bioassays and long turnaround time could severely affect the disease surveillance and control especially in pandemics such as influenza and COVID-19. In view of this, a portable, quantitative bioassay device will be valuable in regions with scarce medical resources and help relieve burden on local healthcare systems. Herein, we introduce the MagiCoil diagnostic device, an inexpensive, portable, quantitative and rapid bioassay platform based on magnetic particle spectrometer (MPS) technique. MPS detects the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses the harmonics from oscillating MNPs as metrics for sensitive and quantitative bioassays. This device does not require trained technicians to operate and employs a fully automatic, one-step, wash-free assay with user friendly smartphone interface. Using a streptavidin-biotin binding system as a model, we show that the detection limit of the current portable device for streptavidin is 64 nM (equal to 5.12 pmole). In addition, this MPS technique is very versatile and allows for the detection of different diseases just by changing the surface modifications on MNPs. It’s foreseen that this kind of portable device can transform the multi-step, laboratory-based bioassays to one-step field testing in non-clinical settings such as schools, homes, offices, etc. © 2020, CC BY.

关键词： Diagnosis

Magnetic Control of Soft Chiral Phonons in PbTe

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Physical Review Letters 2022年第7期128卷 075901-075901页

作者： Andrey Baydin Felix G. G. Hernandez Martin Rodriguez-Vega Anderson K. Okazaki Fuyang Tay G. Timothy Noe, II Ikufumi Katayama Jun Takeda Hiroyuki Nojiri Paulo H. O. Rappl Eduardo Abramof Gregory A. Fiete Junichiro Kono Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Smalley-Curl Institute Rice University Houston Texas 77005 USA Instituto de Física Universidade de São Paulo São Paulo São Paulo 05508-090 Brazil Theoretical Division Los Alamos National Laboratory Los Alamos New Mexico 87545 USA Laboratório Associado de Sensores e Materiais Instituto Nacional de Pesquisas Espaciais São José dos Campos São Paulo 12201-970 Brazil Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama 240-8501 Japan Institute for Materials Research Tohoku University Sendai 980-8577 Japan Department of Physics Northeastern University Boston Massachusetts 02115 USA Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics and Astronomy Rice University Houston Texas 77005 USA Department of Material Science and NanoEngineering Rice University Houston Texas 77005 USA

PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term. In magnetic fields up to 25 T, the phonon mode splits into two modes with opposite handedness, exhibiting circular dichroism. Their frequencies display Zeeman splitting together with an overall diamagnetic shift with increasing magnetic field. Using a group-theoretical approach, we demonstrate that these observations are the result of magnetic field-induced morphic changes in the crystal symmetries through the Lorentz force exerted on the lattice ions. Thus, our Letter reveals a novel process of controlling phonon properties in a soft ionic lattice by a strong magnetic field.

关键词： Chirality Diamagnetism Magneto-dielectric effect Optical phonons Thermal conductivity Zeeman effect Terahertz time-domain spectroscopy

Diamond Surface Functionalization via Visible Light-Driven C-H Activation for Nanoscale Quantum Sensing

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arXiv 2023年

作者： Rodgers, Lila V.H. Nguyen, Suong T. Cox, James H. Zervas, Kalliope Yuan, Zhiyang Sangtawesin, Sorawis Stacey, Alastair Jaye, Cherno Weiland, Conan Pershin, Anton Gali, Adam Thomsen, Lars Meynell, Simon A. Hughes, Lillian B. Bleszynski Jayich, Ania C. Gui, Xin Cava, Robert J. Knowles, Robert R. de Leon, Nathalie P. Princeton University Department of Electrical and Computer Engineering PrincetonNJ08540 United States Princeton University Department of Chemistry PrincetonNJ08540 United States School of Physics Center of Excellence in Advanced Functional Materials Suranaree University of Technology Nakhon Ratchasima30000 Thailand School of Physics University of Melbourne ParkvilleVIC3010 Australia School of Science RMIT University MelbourneVIC3000 Australia Material Measurement Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Wigner Research Centre for Physics POB 49 BudapestH-1525 Hungary Department of Atomic Physics Budapest University of Technology and Economics Műegyetem rakpart 3. BudapestH-1111 Hungary Australian Synchrotron Australian Nuclear Science and Technology Organisation 800 Blackburn Road ClaytonVIC3168 Australia Physics Department University of California Santa Barbara Santa BarbaraCA93106 United States Materials Department University of California Santa Barbara Santa BarbaraCA93106 United States

Nitrogen-vacancy (NV) centers in diamond are a promising platform for nanoscale nuclear magnetic resonance (NMR) sensing1. Despite significant progress towards using NV centers to detect and localize nuclear spins down to the single spin level2,3, NV-based spectroscopy of individual, intact, arbitrary target molecules remains elusive. NV molecular sensing requires that target molecules are immobilized within a few nanometers of NV centers with long spin coherence time. The inert nature of diamond4 typically requires harsh functionalization techniques such as thermal annealing2,5 or plasma processing6–8, limiting the scope of functional groups that can be attached to the surface. Solution-phase chemical methods can be more readily generalized to install diverse functional groups, but they have not been widely explored for single-crystal diamond surfaces. Moreover, realizing shallow NV centers with long spin coherence times requires highly ordered single-crystal surfaces, and solution-phase functionalization has not yet been shown to be compatible with such demanding conditions. In this work, we report a versatile strategy to directly functionalize C–H bonds on single-crystal diamond surfaces under ambient conditions using visible light. Hydrogen atom abstraction from surface C–H bonds generates carbon-centered radicals that can either intercept various radical acceptors or be oxidized to carbocations to form C–F, C–Cl, C–S, and C–N bonds at the surface. We verify covalent bond formation using lab and synchrotron-based surface analysis. This functionalization method is compatible with charge stable NV centers within 10 nm of the surface with spin coherence times comparable to the state of the art5. As a proof of principle, we use shallow ensembles of NV centers to detect nuclear spins from functional groups attached to the surface. Our approach to surface functionalization based on visible light-driven C–H bond activation opens the door to deploying NV centers as a br

关键词： Chemical activation

Applications of nanomagnets as dynamical systems

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arXiv 2021年

作者： Rana, Bivas Mondal, Amrit Kumar Bandyopadhyay, Supriyo Barman, Anjan Center for Emergent Matter Science RIKEN 2-1 Hirosawa Wako351-0198 Japan Faculty of Physics Adam Mickiewicz University Poznań Uniwersytetu Poznanskiego 2 Poznań61-614 Poland Department of Condensed Matter Physics and Material Sciences S. N. Bose National Centre for Basic Sciences Block JD Sector III Salt Lake Kolkata700 106 India Department of Electrical and Computer Engineering Virginia Commonwealth University RichmondVA23284 United States

When magnets are fashioned into nanoscale elements, they exhibit a wide variety of phenomena replete with rich physics and the lure of tantalizing applications. In this topical review, we discuss some of these phenomena, especially those that have come to light recently, and highlight their potential applications. We emphasize what drives a phenomenon, what undergirds the dynamics of the system that exhibits the phenomenon, how the dynamics can be manipulated, and what specific features can be harnessed for technological advances. For the sake of balance, we point out both advantages and shortcomings of nanomagnet based devices and systems predicated on the phenomena we discuss. Where possible, we chart out paths for future investigations that can shed new light on an intriguing phenomenon and/or facilitate both traditional and non-traditional applications. Copyright © 2021, The Authors. All rights reserved.

关键词： Magnetization reversal

Adiabatic mode transformation in width-graded nano-gratings: enabling multiwavelength light localization

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arXiv 2020年

作者： Shayegannia, Moein Montazeri, Arthur O. Dixon, Katelyn Prinja, Rajiv Kazemi-Zanjani, Nastaran Kherani, Nazir P. Department of Electrical and Computer Engineering University of Toronto TorontoONM5S 3G4 Canada Department of Material Science & Engineering University of Toronto TorontoONM5S 3E4 Canada Lawrence Berkeley National Laboratory 1 Cyclotron Rd. BerkeleyCA94720 United States

We delineate the four principal surface plasmon polariton coupling and interaction mechanisms in subwavelength gratings, and demonstrate their significant roles in shaping the optical response of plasmonic gratings. Within the framework of width-graded metal-insulator-metal nano-gratings, mode confinement and wave guiding result in multiwavelength light localization provided conditions of adiabatic mode transformation are satisfied. The field is enhanced further through fine tuning of the groove-width (w), groove-depth (L) and groove-to-groove-separation (d). By juxtaposing the resonance modes of width-graded and non-graded gratings and defining the adiabaticity condition, we demonstrate the criticality of w and d in achieving adiabatic mode transformation among the grooves. We observe that the resonant wavelength of a graded grating corresponds to the properties of a single groove when the grooves are adiabatically coupled. We show that L plays an important function in defining the span of localized wavelengths. We show that multiwavelength resonant modes with intensity enhancement exceeding 3 orders of magnitude are possible with w Copyright © 2020, The Authors. All rights reserved.

关键词： Electromagnetic wave polarization

Extreme sub-wavelength magneto-elastic electromagnetic antenna implemented with multiferroic nanomagnets1

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arXiv 2020年

作者： Drobitch, J.L. De, A. Dutta, K. Pal, P. Adhikari, A. Barman, A. Bandyopadhyay, S. Dept. of Electrical and Computer Engineering Virginia Commonwealth University RichmondVA23284 United States Dept. of Condensed Matter Physics and Material Science S. N. Bose National Center for Basic Sciences JD Block Sector III Salt Lake Kolkata700 106 India

Antennas typically have emission/radiation efficiencies bounded by A λ 2 ( A2 ) where A is the emitting area and λ is the wavelength of the emitted wavelength. That makes it challenging to miniaturize antennas to extreme sub-wavelength dimensions. One way to overcome this challenge is to actuate an antenna not at the resonance of the emitted wave, but at the resonance of a different excitation that has a much shorter wavelength at the same frequency. We have actuated an electromagnetic (EM) antenna with a surface acoustic wave (SAW) whose wavelength is about five orders of magnitude smaller than the EM wavelength at the same frequency. This allowed us to implement an extreme sub-wavelength EM antenna, radiating an EM wave of wavelength λ = 2 m, whose emitting area is ~10-8 m2 (A λ 2 = 2.5 x 10-9), and whose measured radiation efficiency exceeded the A λ 2 limit by over 105. The antenna consisted of magnetostrictive nanomagnets deposited on a piezoelectric substrate. A SAW launched in the substrate with an alternating electrical voltage periodically strained the nanomagnets and rotated their magnetizations owing to the Villari effect. The oscillating magnetizations emitted EM waves at the frequency of the SAW. These extreme sub-wavelength antennas, that radiate with efficiencies a few orders of magnitude larger than the A λ 2 limit, allow drastic miniaturization of communication systems. Copyright © 2020, The Authors. All rights reserved.

关键词： Antennas

Design of infrared microspectrometers based on phase-modulated axilenses

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arXiv 2020年

作者： Chen, Yuyao Britton, Wesley A. Negro, Luca Dal Department of Electrical & Computer Engineering and Photonics Center Boston University 8 Saint Marys Street BostonMA02215 United States Division of Material Science and Engineering Boston University 15 Saint Marys Street BrooklineMA02446 United States Department of Physics Boston University 590 Commonwealth Avenue BostonMA02215 United States

We design and characterize a novel axilens-based diffractive optics platform that flexibly combines efficient point focusing and grating selectivity and is compatible with scalable top-down fabrication based on a 4-level phase mask configuration. This is achieved using phase-modulated compact axilens devices that simultaneously focus incident radiation of selected wavelengths at predefined locations with larger focal depths compared to traditional Fresnel lenses. In addition, the proposed devices are polarization insensitive and maintain a large focusing efficiency over a broad spectral band. Specifically, here we discuss and characterize modulated axilens configurations designed for long-wavelength infrared (LWIR) in the 6 µm–12 µm wavelength range and in the 4 µm–6 µm mid-wavelength infrared (MWIR) range. These devices are ideally suited for monolithic integration atop the substrate layers of infrared focal plane arrays (IR-FPAs) and for use as compact microspectrometers. We systematically study their focusing efficiency, spectral response, and cross talk ratio, and we demonstrate linear control of multi-wavelength focusing on a single plane. Our design method leverages Rayleigh-Sommerfeld (RS) diffraction theory and is validated numerically using the Finite Element Method (FEM). Finally, we demonstrate the application of spatially modulated axilenses to the realization of compact, single-lens spectrometer. By optimizing our devices, we achieve a minimum distinguishable wavelength interval of ∆λ = 240nm at λc = 8µm and ∆λ = 165nm at λc = 5µm. The proposed devices add fundamental spectroscopic capabilities to compact imaging devices for a number of applications ranging from spectral sorting to LWIR and MWIR phase contrast imaging and detection. Copyright © 2020, The Authors. All rights reserved.

关键词： Focusing