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  • Synthesis, crystal structure and optical properties of Anderson-type heteropolyanion with cobalt cations
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Yassine Ammari, S. Abid, K. Horchani Naifer

    A sample inorganic A-type Anderson polyoxometalate (POM) (TeMo6) compound formulated as [Co(H2O)6]3[TeMo6O24] is synthesized in aqueous solution by slow evaporation technique. Single-crystal X-ray diffraction analysis reveals that the obtained compound crystallizes in the centrosymmetric hexagonal space group (R-3c) with a formula unit made up of one [TeMo6O24]6− A-type Anderson anion and three [Co(H2O)3]2+ cations. The molecular Hirshfeld surface indicates that the crystal packing is stabilized by H-bonds interactions to generate 3D supramolecular frameworks. Furthermore, some optical properties such as bandgap energy, refractive index, dielectric constant and optical conductivity of the sample are investigated. The large value of refractive index known in the visible region of electromagnetic spectrum (n = 3.5 at 1.8 eV) reveals that this sample can become a promising candidate for visible optical communication devices. The emission fluorescent spectrum in the solid state at room temperature is measured and the decay lifetime curves are obtained by monitoring the ligand-to-metal charge transfer transition (LMCT). The studies of the colorimetric properties of the sample reveal that the color coordinates (x = 0.33667; y = 0.25564) are located in the region of National Television System Committee (NTSC) in the CIE chromaticity chart and the calculated correlated color temperature value (CCT ~ 5085 K) indicates that the optimized compound could be applied as a cool light emission diode.

    更新日期:2020-01-16
  • Microstructure and dielectric properties of LiTaO 3 ceramics with MnO 2 addition fabricated by hot-pressing sintering
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Qiang Zheng, Youfeng Zhang

    Abstract Lithium tantalite (LiTaO3) is an excellent single crystal, only a few studies focused on polycrystalline LiTaO3 ceramics, because it is difficult to sintering densification in fabrication process by common sintering. In this paper, LiTaO3 composite ceramics with added 3 wt% MnO2 were obtained by hot-pressing sintering at different temperatures from 1200 to 1350 °C. The sinterability, microstructure and dielectric properties of LiTaO3 ceramics fabricated at sintering temperatures were investigated. The relative density of the LiTaO3 ceramics was significantly enhanced as the sintering temperature increases first and then decreased. The LiTaO3 ceramics achieved the highest relative density (98.6%) and shown homogeneous microstructure when sintered at 1300 °C. The LiTaO3 and manganese oxide phases were observed in the MnO2/LiTaO3 ceramics fabricated at different sintering temperatures. The dielectric properties of MnO2/LiTaO3 ceramics were significantly influenced by the sintering temperatures. The study of dielectric properties revealed that the specimen had excellent dielectric properties when sintering temperature was 1300 °C and the dielectric constant was 78, as it tends to stay invariable at room temperature.

    更新日期:2020-01-16
  • Caloric and isothermal equations of state of solids: empirical modeling with multiply broken power-law densities
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Roman Tomaschitz

    Empirical equations of state (EoSs) are developed for solids, applicable over extended temperature and pressure ranges. The EoSs are modeled as multiply broken power laws, in closed form without the use of ascending series expansions; their general analytic structure is explained and specific examples are studied. The caloric EoS is put to test with two carbon allotropes, diamond and graphite, as well as vitreous silica. To this end, least-squares fits of broken power-law densities are performed to heat capacity data covering several logarithmic decades in temperature, the high- and low-temperature regimes and especially the intermediate temperature range where the Debye theory is of limited accuracy. The analytic fits of the heat capacities are then temperature integrated to obtain the entropy and caloric EoS, i.e. the internal energy. Multiply broken power laws are also employed to model the isothermal EoSs of metals (Al, Cu, Mo, Ta, Au, W, Pt) at ambient temperature, over a pressure range up to several hundred GPa. In the case of copper, the empirical pressure range is extended into the TPa interval with data points from DFT calculations. For each metal, the parameters defining the isothermal EoS (i.e. the density–pressure relation) are inferred by nonlinear regression. The analytic pressure dependence of the compression modulus of each metal is obtained as well, over the full data range.

    更新日期:2020-01-16
  • A comparative study of the structural, magnetic transport and electrochemical properties of La 0.7 Sr 0.3 MnO 3 synthesized by different chemical routes
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Kumar Navin, Rajnish Kurchania

    A comparative study of the structural, magnetic, transport and electrochemical properties of the La0.7Sr0.3MnO3 (LSMO) synthesized by sol–gel, solution combustion and solid-state reaction has been discussed in details. Synthesis process controls the structure and morphology of the material which determine the overall characteristics of the material. The sol–gel and solution combustion method provide nanocrystalline material with an average particle size of 23.03 nm 17.9 nm, respectively; while, microcrystalline material with an average particle size of 160 nm is synthesized by solid-state reaction method. The magnetic properties of the material are improved with an increase in particle size from nanoscale to microscale, while resistivity increases with a reduction in the size of the material. The LSMO synthesized by the sol–gel method shows the highest magnetoresistance of 32.3% at 10 K with a 1T magnetic field. The solution combustion method provides LSMO nanoparticles with large surface area and porosity which results in its better electrochemical behavior as compared to the LSMO synthesized by sol–gel and solid-state reaction.

    更新日期:2020-01-16
  • Facile preparation of ZnO nanostructured thin films via oblique angle ultrasonic mist vapor deposition (OA-UMVD): a systematic investigation
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-16
    Hassan Alehdaghi, Maziyar Kazemi, Mohammad Zirak

    Ultrasonic mist vapor deposition (UMVD) is a widely used facile technique to prepare ZnO thin films. The surface properties of prepared thin films can be tuned via easily controllable UMVD deposition parameters. Herein, we utilized an oblique angle (OA) geometry in UMVD system named as OA-UMVD. The angle between incident flow and substrate (θs) was changed from 0° to 45°. Alteration of θs as well as substrate temperature (Ts) resulted in the deposition of ZnO thin films with different morphologies. For mild nozzle–substrate distance (D = 3 cm), fine vertical ZnO nanosheets with length of 123 nm and thickness of 23 nm were obtained for low Ts (330 °C) and small θs (≈ 0°). By increasing both Ts and θs, ZnO nanorods gradually appeared on the surface. Both nozzle–substrate distance (D) and Ts showed similar effect on deposition rate (Rd), and Rd decreased by increase of D and Ts, while deposition rate increased for larger θs. Confocal microscopy results revealed that using low Ts (330 °C), short distance (D = 1.5 cm) and large θs (45°) resulted in high macroscopic surface roughness (MRs) of 98 nm, while high Ts (500 °C), long D (5 cm) and small θs (≈ 0○) created compact and smooth surface with low MRs of 5 nm, in accordance with transmittance results. The ZnO wurtzite crystal structure was approved via X-ray diffraction patterns. The crystallite size in the layers was affected only by Ts, and θs had no significant effect on the layers’ crystallinity. Obtaining different ZnO nanostructures with different MRs via easily and accurately controllable growth parameters is a great advantage for our employed OA-UMVD system, which could be used to prepare ZnO thin films with desired morphologies for widespread application fields.

    更新日期:2020-01-16
  • Optically triggered chaotic vortex avalanches in superconducting YBa2Cu3O7−xfilms
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    You-He Zhou, Cunhong Wang, Cong Liu, Huadong Yong, and Xingyi Zhang

    Flux avalanche is commonly found in type-II superconductors, and this event is always featured as unpredictable and ultra-fast development with time. It is difficult to be captured dynamically by any experimental method available today. In this letter, we firstly propose a hypervelocity magnetic-optical system with two optical branches; one branch can trigger a dendritic flux avalanche in a superconducting film, and the other is capable of producing continuous multiexposure} to record the lightning avalanche process In contrast with some traditional trigger models, the present method realizes control of the position where the flux avalanche takes place. Second, we study the sensitive dependence on initial conditions} (SDIC) of the present flux avalanche for the first time and find series of positive Lyapunov exponents} between two adjacent trajectories which could be considered direct evidence for the chaotic dynamics in this kind of avalanche. Moreover, we reveal that whether the laser spot is in the Meissner state or the mixed state, avalanches always penetrate from the edge of the superconducting film to the Meissner region instead of occurring around the laser spot. This behavior clearly demonstrates the presented avalanche is driven by the magnetic pressure force}, suggesting that the optically triggered vortex avalanche possesses a new mechanism other than the thermomagnetic avalanches that are commonly found in superconducting films.

    更新日期:2020-01-16
  • Quantum pure state tomography via variational hybrid quantum-classical method
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Tao Xin, Xinfang Nie, Xiangyu Kong, Jingwei Wen, Dawei Lu, and Jun Li

    To obtain a complete description of a quantum system, one usually employs standard quantum state tomography, which however requires exponential number of measurements to perform and hence is impractical when the system’s size grows large. In this work, we introduce a self-learning tomographic scheme based on the variational hybrid quantum-classical method. The key part of the scheme is a learning procedure, in which we learn a control sequence capable of driving the unknown target state coherently to a simple fiducial state, so that the target state can be directly reconstructed by applying the control sequence reversely. In this manner, the state tomography problem is converted to a state-to-state transfer problem. To solve the latter problem, we use the closed-loop learning control approach. Our scheme is further experimentally tested using techniques of a 4-qubit nuclear magnetic resonance. \red{Experimental results indicate that the proposed tomographic scheme can handle a broad class of states including entangled states in quantum information, as well as dynamical states of quantum many-body systems common to condensed matter physics.

    更新日期:2020-01-16
  • Autotuning of double-dot devicesin situwith machine learning
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Justyna P. Zwolak, Thomas McJunkin, Sandesh S. Kalantre, J. P. Dodson, E. R. MacQuarrie, D. E. Savage, M. G. Lagally, S. N. Coppersmith, Mark A. Eriksson, and Jacob M. Taylor

    The current practice of manually tuning quantum dots (QDs) for qubit operation is a relatively time-consuming procedure inherently impractical for scaling up and applications. In this work, we report on the {} implementation of a recently proposed auto-tuning protocol that combines machine learning (ML) with an optimization routine to navigate the parameter space. In particular, we show that a ML algorithm trained using exclusively simulated data to quantitatively classify the state of double QD device can be used to replace human heuristics in tuning of gate voltages in real devices. We demonstrate active feedback of a functional double dot device operated at millikelvin temperatures and discuss success rates as a function of initial conditions and device performance. Modifications to the training network, fitness function, and optimizer are discussed as a path towards further improvement in the success rate when starting both near and far detuned from the target double dot range.

    更新日期:2020-01-16
  • Effect of microwaves on superconductors for kinetic inductance detection and parametric amplification
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    A. V. Semenov, I. A. Devyatov, M. P. Westig, and T. M. Klapwijk

    We address, using concepts of the microscopic theory of superconductivity, parametric amplifiers and kinetic inductance detectors focusing on the interaction of microwave radiation with the superconducting condensate. This interaction was identified, in recent experiments, as the source of the apparent dissipation in microwave superconducting micro-resonators at low temperatures. Since the evaluation of the performance of practical devices based only on the change in kinetic inductance is not sufficiently informative about the underlying physical processes, we design an experiment with a tunnel-measurement of a microwave-driven superconducting wire, in which the tunnel-process is not affected by the microwaves. We conclude that such an experiment is feasible with the current technology, unfortunately difficult to incorporate in standard superconducting resonators optimized for applied performance. Nevertheless, given the limits of the commonly used phenomenological theories, such an experiment will provide the groundwork for further optimisation of the performance.

    更新日期:2020-01-16
  • Universal output characteristics of single-mode operation in low-loss large-V-number multimode waveguide lasers with transverse spatial hole burning
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Chaofan Wang, Fatemeh HadavandMirzaee, and Tsing-Hua Her

    We study the performance limit of single-mode operation in low-loss, large-V-number, planar waveguide lasers with transverse spatial hole burning as the dominating mechanism for transverse mode competition. By introducing normalized variables, we develop a simple semi-analytical model to describe universal output characteristics of singlemode emission before the onset of the high-order modes, which can be easily scaled to a wide range of laser configuration parameters. Our model is validated using exact numerical solutions which shows applicability beyond the low-loss approximation. Our analysis establishes a minimum criterion of the loss ratio between the fundamental and 1st higher-order mode for a robust single-mode operation. This criterion is much weaker than the conventional wisdom based on pure wave propagation argument which we attribute to a resonator enhancement effect. Our universal outcome can be denormalized to establish the relationship between single-mode extraction efficiency and optimum output coupling in a multimode laser with arbitrary modal loss ratios over a wide range of single-pass unsaturated gain and loss.

    更新日期:2020-01-16
  • Huygens’ metasurfaces based on congener dipole excitations
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Tianhua Feng, Alexander A. Potapov, Zixian Liang, and Yi Xu

    Huygens’ metasurfaces provide a versatile and efficient platform for exotic wave manipulation. Conventional transmissive Huygens’ metasurfaces rely on the interference between different multipole excitations to minimize the undesired reflection, but the different nature between multipoles introduces challenge on the bandwidth and practical applications. Here, we reveal that in contrast to the conventional scheme, exciting congener dipoles within the same multipole catalogue is also possible to realize high-efficiency broadband Huygens’ metasurfaces for linearly polarized light. A theoretical model has been proposed and the required conditions for zero reflection and 2π phase variation have been derived in the dipole approximation. This model has been validated by a silicon dual-nanodisk metasurface, and the beam deflection and focusing functionalities have also been demonstrated with high efficiency and broadband properties.

    更新日期:2020-01-16
  • Linear and nonlinear elastic waves in magnetogranular chains
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    F. Allein, V. Tournat, V. Gusev, and G. Theocharis

    We study a magneto-granular chain composed of stainless steel beads which are placed inside a properly designed periodic magnetic field. The latter provides attractive forces between the particles, leading to a stable structure, free of mechanical boundaries. Using a scanning laser-based probe at the individual-particle level, we observe experimentally, the propagation of longitudinal as well as transverse/rotation waves. In addition, we obtain the dispersion band diagram. In the linear regime, these observations are well supported by a mass-spring model that takes into account both a normal and a shear mechanical coupling between the beads considering translational and rotational degrees of freedom. In the weakly nonlinear regime, we present experimental results including the beating in amplitude of the second harmonic for the longitudinal waves and propagation under oblique driving excitation. A theoretical model that takes into account the Hertzian contact mechanics, dissipation and the finite size of the system, captures well the results of the second harmonic generation for the longitudinal waves. This magneto-sensitive system offers great freedom to design complex waveguide geometries where the interplay between geometry, wave polarization and nonlinearity may pave the way toward the development of advanced signal processing elastic devices.

    更新日期:2020-01-16
  • Symphotic multiplexing medium at microwave frequencies
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Divya Pande, Jonah Gollub, Roberto Zecca, Daniel L. Marks, and David R. Smith

    As opposed to metasurfaces, which can produce a single output waveform in response to a single input waveform, volumetric metamaterials have the ability to perform independent functions on many distinct input waveforms. Here, we present an experimental demonstration of this multiplexing capability using a volumetric metamaterial designed using the symphotic method. The symphotic method realizes highly efficient multiplexing structures in the strong scattering limit. In contrast to perturbative design methods like volume holography that are only applicable in weakly scattering media, we provide a comprehensive approach that takes into consideration design and fabrication constraints and which can be verified in simulations. We then demonstrate an experimental realization of a symphotic device operating at a frequency of 10 GHz, which has been optimized for three distinct input waveforms corresponding to three distinct output waveforms. The device is realized using a low-loss 3D-printed material. The symphotic device consists of a lattice of dielectric cylindrical elements with varying radii, excited in a parallel-plate waveguide to enforce two-dimensional field symmetry. The experimental results show excellent agreement with analytical coupled-dipole method simulations and finite-element simulations. The experiments further demonstrate the scalability of symphotic metamaterials and their viability for advanced RF and optical devices.

    更新日期:2020-01-16
  • Correction to: Low-temperature metal-induced crystallization of hydrogenated amorphous Si 1−x Ge x (0.25 ≤ x ≤ 1) thin films with Au solution
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-15
    Shanglong Peng, Xiaoyan Shen, Deyan He

    Unfortunately, Fig 6 in the article was incorrect.

    更新日期:2020-01-15
  • Spectroscopy of Nanoparticles without Light
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-15
    Johannes Fiedler, Clas Persson, and Stefan Yoshi Buhmann
    更新日期:2020-01-15
  • Photopatterning DNA Structures with Topological Defects and Arbitrary Patterns Through Multiple Length Scales
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-15
    Netra Prasad Dhakal, Jinghua Jiang, Yubing Guo, and Chenhui Peng
    更新日期:2020-01-15
  • Suppression of dynamically induced stochastic magnetic behavior through materials engineering
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    T. J. Broomhall, A. W. Rushforth, M. C. Rosamond, E. H. Linfield, and T. J. Hayward

    Stochastic behaviour fundamentally limits the performance and reliability of nanomagnetic devices. Typically, stochastic behaviour is assumed to be the result of simple thermal activation, but it may also be “dynamically-induced” i.e. a direct result of the spatial and temporal complexity of magnetisation dynamics. In this paper, we show how materials engineering can be used to comprehensively suppress dynamically induced stochasticity. Using the dynamics of magnetic domain walls in Ni80Fe20 nanowires as a case study we show how manipulation of the Gilbert damping constant via doping with the rare earth element Terbium dramatically simplifies domain wall dynamics. This allows us to obtain quasi-deterministic behaviours from systems that nominally exhibit exceptionally high levels of stochasticity.

    更新日期:2020-01-15
  • Mass loss from a stretching semitransparent sheet of liquid tin
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Bo Liu, Dmitry Kurilovich, Hanneke Gelderblom, and Oscar O. Versolato

    We experimentally study the morphology of a radially expanding sheet of liquid tin, formed by nanosecond-pulse Nd:YAG laser impact on a spherical microdroplet. Specifically, the sheet thickness profile and its time evolution are captured in detail over a range of laser-pulse energies and for two droplet sizes. Two complementary methods to determine this thickness are employed and shown to be in excellent agreement. All obtained thickness profiles collapse onto a single self-similar curve. Spatial integration of the thickness profiles allows determining the volume of the sheet. Remarkably, less than half of the initial amount of tin remains in the sheet under conditions relevant for industrial sources of extreme ultraviolet light, where these thin tin sheets serve as target material. Further analysis shows that the dominant fraction of the mass lost from the sheet during its expansion ends up as fine fragments. We propose that such mass loss can be minimized by producing the sheet targets on the shortest possible timescale. These findings are particularly valuable for ongoing developments in state-of-the-art nanolithography.

    更新日期:2020-01-15
  • Collective Resonances of a Chain of Coupled Phononic Microresonators
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-14
    Ting-Ting Wang, Sylwester Bargiel, Franck Lardet-Vieudrin, Yan-Feng Wang, Yue-Sheng Wang, and Vincent Laude
    更新日期:2020-01-15
  • Topological Edge States in Quasiperiodic Locally Resonant Metastructures
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-14
    Yiwei Xia, Alper Erturk, and Massimo Ruzzene
    更新日期:2020-01-15
  • Ultralow Surface Resistance via Vacuum Heat Treatment of Superconducting Radio-Frequency Cavities
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-14
    S. Posen, A. Romanenko, A. Grassellino, O.S. Melnychuk, and D.A. Sergatskov
    更新日期:2020-01-15
  • Spontaneous phase and frequency locking of transverse modes in different orders
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Zilong Zhang and Changming Zhao

    Transverse mode locking is repaid attention recently due to its combination with the optical vortices’ formation. In the previous investigations, transverse mode locking is only focused on the phase locking of modes in different orders to research the beam pattern dynamics, or between frequency-degenerated transverse modes to form a spatial stationary beam pattern with optical vortices. It’s experimentally shown that phase and frequency locking between transverse modes in non-frequency degenerated families can be obtained by microchip cavities with high nonlinearity. And we also point out that, for a both temporal and spatial stationary composed beam pattern formed by transverse mode locking, not only the frequency but also the propagation parameters of the beam should be coupled.

    更新日期:2020-01-15
  • Enhancing the speed and sensitivity of a nonlinear optical sensor with noise
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Said R. K. Rodriguez

    We demonstrate how noise can be turned into a resource} for optical sensing using a nonlinear cavity. The cavity is driven by a continuous wave laser into the regime of optical bistability. Due to the influence of fluctuations, the cavity randomly switches between two meta-stable} states. By analyzing residence times in these two states, perturbations to the resonance frequency of the cavity can be detected. Here, such an analysis is presented as a function of the strength of the perturbation and of the noise. By increasing the standard deviation of the noise, we find that the detection speed increases monotonically while the sensitivity peaks at a finite value of the noise strength. Furthermore, we discuss how noise-assisted sensing can be optimized in state-of-the-art experimental platforms, relying solely on the minimum amount of noise present in the cavity due to its dissipation. These results open new perspectives for the ultrafast detection of nanoparticles, contaminants, gases, or other perturbations to the resonance frequency of an optical resonator, at low powers and in noisy environments.

    更新日期:2020-01-15
  • Synthesis of cesium tungsten bronze by a solution-based chemical route and the NIR shielding properties of cesium tungsten bronze thin films
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    Pin-Jhen Wu, Sanjaya Brahma, Horng-Hwa Lu, Jow-Lay Huang

    Abstract In this study, hexagonal Cs0.32WO3 powders were synthesized by a simple solution-based chemical route. The experiment can be performed within a relatively short time and can easily produce large amounts of hexagonal Cs0.32WO3 powders. The CsxWO3 powders as synthesized and after heat treatment were characterized by X-ray diffraction, scanning electron microscopy, differential thermal and thermogravimetric analysis and Fourier transform infrared spectroscopy. CsxWO3 thin films were deposited by an electron beam evaporation method from sintered Cs0.32WO3 powders as the targets. The CsxWO3 films were annealed at different temperatures under Ar and Ar/H2 atmospheres. The effects of annealing on the microstructure, morphology and near-infrared (NIR) shielding properties of the Cs0.32WO3 films are discussed. The results show that the Cs0.32WO3 thin film specimen annealed for 500 °C in an Ar/H2 atmosphere has the highest transmittance (80%) in the visible light region and the lowest transmittance (42%) in the NIR region.

    更新日期:2020-01-14
  • Enrichment of optical, electrical, and magnetic properties of Li + , La 3+ doped BaTiO 3 perovskite multifunctional ceramics
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    K. Madhan, R. Murugaraj

    Abstract Li and La co-doped Ba(1-x)(Lix/2Lax/2)TiO3 (BLLT) ceramics with x = 0.01, 0.02, 0.03, and 0.04 at A—site was synthesized by sol–gel combustion method. The powder X-ray diffraction and Raman analysis showed a good crystalline nature with perovskite tetragonal structure and the grain size of the samples was estimated and compared using a scanning electron microscope. The decreasing trend in the optical band gap upon doping and carrier concentration values was calculated from UV–Vis absorption spectra. Electron paramagnetic resonance g ~ 1.998 for BLLT ceramics confirms that the electrons are localized near oxygen vacancies. The observed signals may be attributed to the reduction of Ti4+/Ti3+ and its related defects. Moreover, the room temperature magnetization versus magnetic field loops showed the mixed weak ferromagnetic and diamagnetic phase. The enhancement of ε′ with respect to the doping of Li and La ion and increase in particle size due to the number of grain boundaries in BLLT ceramics were studied. The polarization versus electric field of BLLT samples indicates the lossy capacitor behavior, which is attributed to the relatively high leakage current caused by the existence of a defect or oxygen vacancies.

    更新日期:2020-01-14
  • Extending bandgap method of concentric ring locally resonant phononic crystals
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    Lijian Lei, Linchang Miao, Chao Li, Xiaodong Liang, Junjie Wang

    Abstract Locally resonant phononic crystals (LRPCs) have the capacity to adjust elastic waves with the structure sizes much smaller than the incident wavelengths, the unique property is called low-frequency bandgap, but it is not easily applied in practical engineering because of narrow bandgap width. Multilayered LRPCs are helpful in generating several bandgaps, in the meanwhile the designs of multilayered LRPCs proposed in previous study result in the larger filling fraction, whereas the bandwidth of LRPCs increases monotonically with filling fraction, thus the pure contribution of concentric ring configuration to the bandwidth extending is less involved. Keeping the filling fraction constant, this paper carefully designs the microstructure of concentric ring locally resonant phononic crystals, and investigates the effects of structure configuration on the bandgap property. To this end, an updated improved plane wave expansion (UIPWE) method is developed to calculate the band structure, and finite element method (FEM) is used to obtain transmission spectra and vibration mode. The results demonstrate that UIPWE method is valid and is able to give precise outcomes, which is verified by FEM. In addition, the concentric ring configuration equivalently produces dual-oscillator system, relative movements between the oscillators generate coupling effect, thus, the bandgaps can be extended by configurating rightly the microstructure of single cell. Further studies about different models indicate that the combination of smaller inner scatterers and larger inner coating layers are beneficial to wider bandgap. These conclusions presented herein provide insights in the design of three-component PCs in multi-frequency vibration control field.

    更新日期:2020-01-14
  • Comparative evaluation of nuclear radiation shielding properties of x TeO 2 + (100– x )Li 2 O glass system
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-14
    M. Kamislioglu, E. E. Altunsoy Guclu, H. O. Tekin

    Abstract In the present investigation, nuclear radiation shielding parameters of xTeO2 + (100–x)Li2O (where x = 95, 90, 85, 80, 75, and 70 mol%) glass system have been examined. Gamma shielding parameters such as mass attenuation coefficients (MAC), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff) were calculated. Moreover, neutron effective cross sections (∑R) are determined. The calculations for present materials have been performed in different photon energy ranges (0.01–20 MeV) and using Monte Carlo N-Particle eXtended (MCNPX) simulation code and theoretical results were also obtained with WinXcom program. The results obtained from the MCNPX and WinXcom program were found to be in well harmony. Moreover, for the assessment of radiation shielding success of tellurite glasses, the mass stopping power (MSP) and projected range (PR) were computed for proton and alpha particles using stopping and range of ions in matter (SRIM) code. When the results obtained from the study are examined, it is seen that 95TeLi glass has the lowest HVL, TVL, MFP, TF and the highest (∑R) values. Therefore, the 95TeLi glass has the most perfect radiation shielding achievement than other investigated glasses.

    更新日期:2020-01-14
  • Ultrathin, highly flexible and optically transparent terahertz polarizer based on transparent conducting oxide
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-14
    Weien Lai, Hao Yuan, Hongyun Fang, Yaohua Zhu and Huizhen Wu

    Multifunctional terahertz devices hold great promise for terahertz (THz) optical systems. Here, we present an ultrathin, highly flexible and optically transparent terahertz polarizer based on tin-doped indium oxide (ITO) and flexible conformal films of polyethylene terephthalate. The flexible optical transparent polarizer (FOTP) was theoretically investigated and experimentally characterized by UV–vis spectrophotometry and THz time-domain system. In the FOTP, THz conductivity of ITO films is mainly dominated by DC conductivity. The FOTP reveals a high optical transmittance of more than 60% in the visible region, a high extinction ratio of about 20 dB in the 0.1 THz–2.5 THz and a low insertion loss below 2 dB in the 0.1 THz–1.4 THz. The proposed FOTP can significantly improve the overall performance of THz optical systems and be easily fabricated by commercial display techniques. Our concept opens up a new window for highly flexible and optically transparent THz devices.

    更新日期:2020-01-14
  • Electron scattering analysis in 2DEG in sputtering-grown MgZnO/ZnO heterostructure
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-14
    Pawan Kumar, Md Arif Khan, Gaurav Siddharth, Sanjay Kumar, Ruchi Singh and Shaibal Mukherjee

    Here, we present an analytical modeling of electron mobility in two dimensional electron gas (2DEG)-yielding MgZnO/ZnO heterostructures, to ascertain dominant scattering mechanisms and physical parameters responsible for one-order lower value of electron mobility in sputtering-grown heterostructure as compared to that in molecular beam epitaxy-grown heterostructure. This work extensively probes all scattering components and their physical parameters, such as dislocation density, impurity density, mole fraction, 2DEG density, correlation length and lateral size, for their respective effects on electron mobility of sputtered heterostructure. The results suggest that dislocation density and alloy disorder scattering are the most dominant sources responsible for reduced electron mobility. This work is extremely crucial for achieving high electron mobility by optimizing the material growth parameters to attain low dislocation density, impurity density and interface roughness, for the...

    更新日期:2020-01-14
  • Enhancement and manipulation of near-field radiative heat transfer using an intermediate modulator
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Y. H. Kan, C. Y. Zhao, and Z. M. Zhang

    Many efforts have been dedicated to enhancing the near-field radiative heat transfer by designing different kinds of geometric shapes or introducing new materials. Besides just improving the heat transfer rate, active and convenient thermal management is also important in micro/nano thermal systems. We show that introducing an intermediate modulator, based on the graphene/hBN/graphene heterostructure, can enhance and manipulate thermal radiative heat transfer without changing the distance or other parameters of the emitter and absorber. Such three-body systems can increase the radiatively exchanged power several times over corresponding two-body counterparts. The introduced modulator can be viewed as a mid-repeater to effectively enhance photon tunneling through evanescent modes. Furthermore, the heat transfer rate could be modulated in a large range and even be lower than two-body systems by applying bias voltages. The mechanism can be explained by the change of energy transmission coefficients between bodies through adjusting the optical properties of graphene. The presented scheme may open a new avenue to actively control near-field heat transfer at the micro/nanoscales.

    更新日期:2020-01-14
  • Simultaneous perfect bending and polarization rotation of electromagnetic wavefront using chiral gradient metasurfaces
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Hamidreza Kazemi, Mohammad Albooyeh, and Filippo Capolino

    We introduce chiral gradient metasurfaces that allow perfect transmission of the incident wave into a desired direction and simultaneous perfect rotation of the polarization of the refracted wave with respect to the incident one. In the lossless limit transmission can reach 100% with a single metasurface layer.} Besides using gradient polarization densities which provide bending of the refracted wave with respect to the incident one, using metasurface inclusions that are chiral allows the polarization of the refracted wave to be rotated. We suggest a possible realization of the proposed device by discretizing the required equivalent surface polarization densities, and synthesizing the chiral discrete polarizabilities with properly sized helical inclusions at each discretization point. By using only a single, optically thin, layer of chiral inclusions, we are able to unprecedentedly deflect a normal incident plane wave to a refracted plane wave at $45\lyxmathsym{\textdegree}$ with 72% power efficiency which is accompanied by a 90∘ polarization rotation. The proposed concepts and design method may find practical applications in polarization rotation devices at microwaves as well as in optics, especially when the incident power is required to be deflected.

    更新日期:2020-01-14
  • Identically sized Co quantum dots on monolayer WS2featuring Ohmic contact
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Weiqing Tang, Mingming Fu, Jiajun Chen, Baofan Sun, Congming Ke, Yaping Wu, Xu Li, Chunmiao Zhang, Zhiming Wu, and Junyong Kang

    Identically-sized Co quantum dots (QDs) are constructed on monolayer tungdten disulfide (WS2) forming coupled heterostructures. Topographical images investigated by in situ scanning tunneling microscopy (STM) show a bias-dependent feature. First-principles calculated binding energies combined with the simulated STM images identify that the Co QDs possess a unique magic number, with a tetrahedral Co4 configuration. Numerical differential conductance measured by scanning tunneling spectroscopy (STS) indicates a p-type doping and an Ohmic contact property for the Co4/WS2 system. Mechanism of the novel transport and conduction properties of the coupled heterostructures is further revealed by analyzing the work functions and interfacial interaction. Our findings offer some references for the controlled fabrication of identically-sized zero-dimensional/two-dimensional (0D/2D) heterostructures and propose a feasible strategy for Ohmic interface contact in nanodevices.

    更新日期:2020-01-14
  • Effect of volume fraction on magnetoelectric coupling effect of Co 0.1 Cu 0.9 Fe 2 O 4 /Ba 0.8 Sr 0.2 TiO 3 composite liquid
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Heng Wu, Ruicheng Xu, Xiaofeng Qin, Rongli Gao, Zhenhua Wang, Chunlin Fu, Wei Cai, Gang Chen, Xiaoling Deng

    Co0.1Cu0.9Fe2O4 (CCFO) and Ba0.8Sr0.2TiO3 (BST) particles were respectively prepared by chemical coprecipitation and hydrothermal method, then CCFO/BST composite liquid was synthesized by distributing surface modified CCFO and Ba0.8Sr0.2TiO3 particles into insulating silicone oil. Effects of volume fraction (ϕv = 1%, 2%, 5% and 10%) on the microstructure, dielectric, ferroelectric and magnetoelectric coupling effect were comparatively investigated. XRD showed that the pure phase of CCFO and BST particles was successfully prepared. CCFO/BST composite particle shows ferromagnetic behavior due to the contribution of magnetic phase CCFO. The dielectric constant of CCFO/BST composite liquid is about 1/25 of the composite particles, and the dielectric constant value of the composite liquid decreases with increasing the volume fraction because the permittivity of silicone oil is far smaller than that of CCFO/BST composite particles. The relative change of dielectric constant of composite liquid under the action of external magnetic field is greater than that of composite particle due to its mobility of particles in liquid. The values of remnant polarization (Pr), coercive field (Ec) and leakage current of CCFO/BST composite liquid increase monotonically with increasing volume fraction, while excessive volume fraction may result in abnormal phenomenon because of the agglomeration of particles. Magnetic field-induced chain structure of the composite liquid has been observed under a light microscope at a magnification of 200. The maximal magnetoelectric (ME) coupling coefficient is about 89.78 V/(cm Oe), which is obtained in the CCFO/BST composite liquid when the volume fraction is 10%.

    更新日期:2020-01-14
  • Experimental study of the diamagnetism and the ferromagnetism in MoS 2 thin films
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Asma Bouarissa, Abdelhamid Layadi, Hager Maghraoui-Meherzi

    Abstract A series of MoS2 films were prepared by the chemical bath deposition method at different temperatures (60–80 °C). The film thicknesses range from 0.988 up to 10.25 µm. The films are polycrystalline. Vibrating sample magnetometer (VSM) was used to study the magnetic properties of these MoS2 films. The experiments were done at room temperature with the magnetic field applied in the film plane. The magnetization curves indicate the coexistence of ferromagnetism and diamagnetism. The saturation and remnant magnetizations, the coercive and saturation fields as well as the diamagnetic susceptibility have been measured and are discussed as a function of the film thickness and the synthesis temperature. A change in the magnetic anisotropy is observed, and the magnetization easy axis direction switches from in-plane to out-of-plane as the thickness increases. The magnetic properties are correlated with the structural ones.

    更新日期:2020-01-14
  • Large Spin Hall Magnetoresistance in Antiferromagneticα−Fe2O3/PtHeterostructures
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-13
    Johanna Fischer, Matthias Althammer, Nynke Vlietstra, Hans Huebl, Sebastian T.B. Goennenwein, Rudolf Gross, Stephan Geprägs, and Matthias Opel
    更新日期:2020-01-14
  • Switchable Assembly and Guidance of Colloidal Particles on an All-Dielectric One-Dimensional Photonic Crystal
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-13
    Fengya Lu, Yan Kuai, Junxue Chen, Xi Tang, Yifeng Xiang, Yang Liu, Pei Wang, Joseph. R. Lakowicz, and Douguo Zhang
    更新日期:2020-01-14
  • Synergistic Effect of Plasma and Laser Processes in Liquid for Alloyed-Nanoparticle Synthesis
    Phys. Rev. Appl. (IF 4.532) Pub Date : 2020-01-13
    Natalie Tarasenka, Alexandre Nominé, Alena Nevar, Mikhail Nedelko, Hiba Kabbara, Stéphanie Bruyère, Jaafar Ghanbaja, Cédric Noel, Andrei Krasilin, George Zograf, Valentin Milichko, Nikita Kulachenkov, Sergey Makarov, Thierry Belmonte, and Nikolai Tarasenko
    更新日期:2020-01-14
  • Precision measurement of the optical conductivity of atomically thin crystals via the photonic spin Hall effect
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Shizhen Chen, Xiaohui Ling, Weixing Shu, Hailu Luo, and Shuangchun Wen

    How to measure the optical conductivity of atomically thin crystals is an important but challenging issue due to the weak light-matter interaction at the atomic scale. Photonic spin Hall effect, as a fundamental physical effect in light-matter interaction, is extremely sensitive to the optical conductivity of atomically thin crystals. Here, we report a precision measurement of the optical conductivity of graphene, where the photonic spin Hall effect acts as a measurement pointer. By incorporating with the weak-value amplification technique, the optical conductivity of monolayer graphene taken as a universal constant of (0.993±0.005)σ0 is detected, and a high measuring resolution with 1.5×10−8Ω−1 is obtained. For few-layer graphene without twist, we find that the conductivities increase linearly with layer number. Our idea could provide an important measurement technique for probing other parameters of atomically thin crystals, such as magneto-optical constant, circular dichroism, and optical nonlinear coefficient.

    更新日期:2020-01-14
  • Comparative study on the physical properties of rare-earth-substituted nano-sized CoFe 2 O 4
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Ebtesam E. Ateia, M. K. Abdelmaksoud, M. M. Arman, Amira S. Shafaay

    Nanotechnology manufacturing is rapidly developing and promises that the essential changes will have significant commercial and scientific impacts be applicable in an extensive range of areas. In this area, cobalt ferrite nanoparticles have been considered as one of the competitive candidates. The present study is based on the investigation of the effect of rare-earth (RE) incorporation on the physical properties of CoFe2O4. Rare-earth ions doped cobalt ferrites with composition CoRE0.025Fe1.975O4 where RE are Ce, Er and Sm have been synthesized by citrate auto combustion technique. Characterization is achieved using X-Ray diffraction (XRD) technique for structural analysis. The obtained data show that the samples exhibit a single-phase spinel structure. RE is successfully substituted into the spinel lattice without any distortion and it acts as inhibiting agent for grain growth. Room temperature M–H curves exhibit ferrimagnetism behavior with a decrease in saturation magnetization and coercivity indicating these materials can be applicable for magnetic data storage and magneto-recording devices. The electrical conductivity is studied as a function of frequency in the temperature range of 300–700 K. The conduction mechanism is attributed to the hopping mechanism. The Seebeck coefficient S is found to be positive for Ce indicating that Co/Ce ferrite behaves as a p-type semiconductor. While it is fluctuated between positive and negative for Er/Sm-doped samples throughout the studied temperature range. The cobalt doped with Er3+ and Sm3+ exhibits degenerated semiconductor trends at higher temperatures. Such data offer a new opportunity for optimizing and improving the performance of cobalt ferrite where the physical properties are decisive.

    更新日期:2020-01-13
  • Toroidal dipole-induced coherent forward scattering from a miniaturized cloaking structure
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    V. P. Sarin, P. V. Vinesh, M. Manoj, C. K. Aanandan, P. Mohanan, K. Vasudevan

    Abstract The physical existence of microwave toroidal dipole in a dogbone metallic inclusion-based miniaturized cloaking structure is verified in this paper. The excitation of toroidal dipole moments on the studied composite is verified using multipole scattering formalism. The presence of the toroidal Fano resonance significantly enhances resonant forward scattering from the structure for normal incidence. Multipolar contribution from the electric, magnetic and toroidal moments significantly enhances the scattering cross-section of the composite as compared to a bare cylindrical metallic object. Applicability of the proposed scheme is tested inside an anechoic chamber using reflection measurements on the fabricated structure and is subsequently validated in computer simulations in the microwave frequency regime.

    更新日期:2020-01-13
  • Strain-tunable band alignment of blue phosphorus–WX 2 ( X = S/Se/Te) vertical heterostructures: from first-principles study
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-13
    Honglin Li, Yuting Cui, Wanjun Li, Lijuan Ye, Lin Mu

    In the scope of two-dimensional (2D) material study, blue phosphorus (BP) is a new graphene-like layered structure that has been successfully synthesized in the experiment after it was theoretically proved to be thermostable. These 2D structured functional materials have great potential in the next-generation nanoscale electronic devices for their unique features. Here, we composite BP and monolayer WX2 (X = S/Se/Te) based on van der Waals force (vdW) interaction to obtain well-defined type-II band alignment heterostructures. A systematic theoretic study was conducted to explore the interlayer coupling effects and the bands’ re-alignment of the BP–WX2 heterostructure after the strain was applied. Nowadays, many researches have proved that 2D materials can be used to degrade pollutants or used as a potential photovoltaic cell material to obtain high performance. We here twist BP and WX2 (X = S/Se/Te) into different angles to lay a theoretical framework on the band alignment and carriers’ separation. It reveals that the electronic properties of freestanding BP and WX2 can be roughly preserved in the corresponding heterostructures. Upon applying strain, band alignment exhibits significant adjustability through varying external strain. The heterostructures are type-II in a certain strain range, within which the carriers can be effectively separated spatially. These heterostructures undergo a transition from semiconductor to metal when a certain strain is imposed. This work not only provides a deep insight into the construction of heterostructures, but presents a new possibility for strain engineering that is both flexible and feasible and can be used for diverse applications.

    更新日期:2020-01-13
  • Exploring the direct effect of intermediate band semiconductor materials on the structural, thermal and optical properties of PMMA nanocomposite
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-11
    M. H. Abdel-Kader, Mohamed Bakr Mohamed

    In this work, polymethylmethacrylate (PMMA) doped with SnS2, Sn0.75Fe0.25S2, and Sn0.75Cr0.25S2 nanoparticles films were prepared using both thermolysis and casting procedures. The purity, structural and shape of the nanofillers were confirmed by Rietveld refinement method. The compositional changes for nanocomposite films were studied by energy dispersive spectrometry technique. Nanoparticles morphology and particle size were examined by transmission electron microscopy (TEM) technique. Proper interactions between added nanofillers and the polymer matrix were discussed in detail by Fourier transform infrared spectroscopy technique (FTIR). The variations in the FTIR absorption bands position and their shape proved the effect of doping on the composite films. The effect of dopant elements on the thermal properties of PMMA polymer matrix has been investigated by thermogravimetric analysis (TGA). Results showed an improvement in the degradation temperature of doped polymers compared to undoped ones. Clear regular arrangements of images for nanoparticles and composite films have been represented by scanning electron microscopy (SEM). Different optical parameters have been examined using UV–vis spectroscopy technique. Due to the high transmittance values in the wavelength range of 320–800 nm, the formed composite films could be used as protective window layers for solar cells. The energy gap values decreased from 4.3 eV for undoped PMMA polymer to 4, 3.85, and 3.16 eV depending on the doping element.

    更新日期:2020-01-13
  • Antimicrobial effects and mechanism of plasma activated fine droplets produced from arc discharge plasma on planktonic Listeria monocytogenes and Escherichia coli O157:H7
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-13
    K H Baek, H I Yong, J H Yoo, J W Kim, Y S Byeon, J Lim, S Y Yoon, S Ryu and C Jo

    In this study, we investigated the antimicrobial effects of plasma activated fine droplet (PAD) produced from arc discharge plasma on planktonic Listeria monocytogenes and Escherichia coli O157:H7. NaCl (0.9%, w/v) was used as the feeding solution for the plasma discharge. The inactivation mechanism of the PAD treatment was also investigated. PAD mainly contains H 2 O 2 and OCl − , which play a significant role in the inactivation process against L. monocytogenes and E. coli O157:H7. The population of L. monocytogenes and E. coli O157:H7 was significantly reduced by approximately 3 and 4 log units, respectively, within 5 min of exposure to PAD. However, the bactericidal effects of PAD against L. monocytogenes and E. coli O157:H7 showed different trends by showing 0.58 and 4.13 log reductions, respectively, after 1 min of PAD exposure time. The change of membrane integrity was evaluated using two ...

    更新日期:2020-01-13
  • Monitoring the evaporation of a sessile water droplet by means of integrated photonic resonator
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-13
    Lucas Garnier, Hervé Lhermite, Véronique Vié, Octave Pin, Quentin Liddell, Hervé Cormerais, Etienne Gaviot and Bruno Bêche

    We have investigated the behavior of the optical transduced signal of a photonic integrated polymer micro resonator as an evaporating water droplet is positioned upon it. The photonic chip is fabricated by means of deep-UV photolithography, and the circuits are made of polymer UV210. The device is then arranged in an optical bench so as to perform relevant measurements thanks to a broadband laser for the excitation of the resonators and an optical spectrum analyzer remotely controlled by a Matlab software for the acquisition and treatment of data. By dynamically tracking the free spectral range (FSR) of the optical mode, we come up with a signature of the thermodynamic evaporation process. In order to correlate this signature to the evaporation speed of the water droplet, a lateral camera is disposed to measure the evolution of the geometrical characteristics of the droplet, while weight measurements are performed thanks to a precision balance. These measurements provide a numer...

    更新日期:2020-01-13
  • Characterization of Komagataeibacter xylinus by a polarization modulation imaging method
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-13
    Weiping Liu, Jichuan Xiong, Heng Zhang, Xuefeng Liu, Gaoshang Liu and Hanwen Zhao

    Komagataeibacter xylinus ( K. xylinus ) has been used for a long time as one of the main cellulose producers among bacterium. In order to gain a better understanding of the physiological and biochemical mechanisms of cellulose production, an efficient and non-invasive visualization method is highly demanded to monitor the morphological changes of K. xylinus during each stage of its development. In this study, a polarization parametric indirect microscopic imaging (PIMI) technique was applied to image the morphology variations of K. xylinus . The optical field with precisely controlled polarization status was incident on the sample and far-field images of the sample were taken under different illumination polarization. In the calculated parametric images, sub-diffraction features related to the morphology details of the K. xylinus were visualized with high contrast and spatial resolution, which is typically irresolvable in conventional microscopic...

    更新日期:2020-01-13
  • Magnetic logic gate based on polarized spin waves
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Weichao Yu, Jin Lan, and Jiang Xiao

    Spin wave, the precession of magnetic order in magnetic materials, is a collective excitation that carries spin angular momentum. Similar to the acoustic or optical waves, the spin wave also possesses the polarization degree of freedom. Although such polarization degrees of freedom are frozen in ferromagnets, they are fully unlocked in antiferromagnets or ferrimagnets. Here we introduce the concept of magnetic gating and demonstrate a spin wave analog of the Datta-Das spin transistor in antiferromagnet. Utilizing the interplay between polarized spin wave and the antiferromagnetic domain walls, we propose a universal logic gate of pure magnetic nature, which realizes all Boolean operations in one single magnetic structure.

    更新日期:2020-01-13
  • Magnetoresistance dynamics in superparamagnetic Co-Fe-B nanodots
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Brad Parks, Ahmed Abdelgawad, Thomas Wong, Richard F. L. Evans, and Sara A. Majetich

    Individual disk-shaped CoFeB nanodots were driven into a superparamagnetic state by spin transfer torque, and their time-dependent magnetoresistance fluctuations were measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations show that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy axis direction. Exchange bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin torque oscillators.

    更新日期:2020-01-13
  • Multimode time-delay interferometer for free-space quantum communication
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Clinton Cahall, Nurul T. Islam, Daniel J. Gauthier, and Jungsang Kim

    Quantum communication schemes such as quantum key distribution (QKD) and superdense teleportation provide unique opportunities to communicate information securely. Increasingly, optical communication is being extended to free-space channels, but atmospheric turbulence in free-space channels requires optical receivers and measurement infrastructure to support many spatial modes. Here we present a multi-mode, Michelson-type time-delay interferometer using a field-widened design for the measurement of phase-encoded states in free-space communication schemes. The interferometer is constructed using glass beam paths to provide thermal stability, a field-widened angular tolerance, and a compact footprint. The performance of the interferometer is highlighted by measured visibilities of 99.02±0.05%, and 98.38±0.01% for single- and multi-mode inputs, respectively. Additionally, high quality multi-mode interference is demonstrated for arbitrary spatial mode structures and for temperature changes of ±1.0∘C. The interferometer has a measured optical path-length drift of 130nm/∘C near room temperature. With this setup, we demonstrate the measurement of a two-peaked, multi-mode, single-photon state used in time-phase QKD with a visibility of 97.37±0.01%.

    更新日期:2020-01-13
  • Three-dimensional mechanistic modeling of gate leakage current in high-κMOSFETs
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Feilong Liu, Yue-Yang Liu, Ling Li, Guofu Zhou, Xiangwei Jiang, and Jun-Wei Luo

    Gate leakage current is a crucial issue for the reliability of modern high-κ MOSFETs. Although various physical models describing both direct tunneling and trap-assisted contribution of leakage current have been presented in literature, many of them treats traps in the dielectric as a continuum distribution in energy and position, and trap-to-trap transport of electrons has so far been mostly neglected or not treated three-dimensionally (3D). In this work, we present a mechanistic model for calculation of gate leakage current in high-κ MOSFET multi-layer stacks based on multi-phonon trap-assisted tunneling theory, taking into account the intrinsic 3D discreteness of traps in the dielectric. Our model can to a good approximation reproduce the experimental results at different dielectric thicknesses, gate voltages, temperatures, and different gate materials. We find that in realistic devices, the 3D trap-to-trap transport of electrons contributes a non-negligible part to the gate leakage current. This contribution is more pronounced at low-voltage device operations, which is important for low-power applications. We calculate the intrinsic fluctuation of gate leakage current due to positional and energetic disorder of traps in the dielectric, and conclude that positional disorder is more important than energetic disorder for realistic material parameters. The calculated gate leakage current depends sensitively on temperature, trap energy, and trap density. We provide a computationally efficient 3D master equation approach that enables 3D mechanistic simulation of 103 traps on the order of minutes on a standard desktop computer.

    更新日期:2020-01-13
  • Room-temperature anisotropic plasma mirror and polarization-controlled optical switch based on type-II Weyl semimetal WP2
    Phys. Rev. Appl. (IF 4.532) Pub Date : 
    Kaixuan Zhang, Yongping Du, Zeming Qi, Bin Cheng, Xiaodong Fan, Laiming Wei, Lin Li, Dongli Wang, Guolin Yu, Shuhong Hu, Changhong Sun, Zhiming Huang, Junhao Chu, Xiangang Wan, and Changgan Zeng

    Anisotropy in electronic structures may ignite intriguing anisotropic optical responses, as well demonstrated in various systems including superconductors, semiconductors and even topological Weyl semimetals. Meanwhile, it is well established in metal optics that the metal reflectance declines from one to zero when the photon frequency is above the plasma frequency ωp, behaving as a plasma mirror. However, the exploration of anisotropic plasma mirrors and corresponding applications remains elusive, especially at room temperature. Here, we discover a pronounced anisotropic plasma reflectance edge in the type-II Weyl semimetal WP2, with an anisotropy ratio of ωp up to 1.5. Such anisotropic plasma mirror behavior and its robustness against temperature promise optical device applications over a wide temperature range. For example, the high sensitivity of polarization-resolved plasma reflectance edge renders WP2 an inherent polarization detector. We further achieve a room-temperature WP2-based optical switch, effectively controlled by simply tuning the light polarization. These findings extend the frontiers of metal optics as a discipline and promise the design of multifunctional devices combining both topological and optical features.

    更新日期:2020-01-13
  • Oxyfluoro-tellurite-zinc glasses and the nuclear-shielding ability under the substitution of AlF 3 by ZnO
    Appl. Phys. A (IF 1.784) Pub Date : 2020-01-10
    M. I. Sayyed, Hakan Akyildirim, M. S. Al-Buriahi, Eloic Lacomme, Rachid Ayad, Giovanni Bonvicini

    This paper examines radiation-shielding abilities of oxyfluoro-tellurite-zinc glasses in the chemical form of AlF3–TeO2–ZnO under the substitution of AlF3 by ZnO. Gamma-ray- and neutron-shielding properties were tested in terms of mass attenuation coefficient (μ/ρ), half value layer, mean free path, effective atomic numbers (Zeff), effective electron density (Neff) and removal cross-section (ΣR). The μ/ρ values of the glasses were generated by Geant4 simulations over an extended energy range and then the generated data were confirmed via XCOM software. The results showed that both gamma-ray- and neutron-shielding efficiencies of the selected glasses evolved by substituting of AlF3 by ZnO. Nuclear radiation-shielding abilities of the current glass systems were compared with that of some conventional shielding materials and newly developed HMO glasses. It can be concluded that oxyfluoro-tellurite-zinc glasses could be useful to design novel shields for radiation protection applications.

    更新日期:2020-01-11
  • Excitation and dissociation of CO 2 heavily diluted in noble gas atmospheric pressure plasma
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-10
    C Stewig, S Schüttler, T Urbanietz, M Böke and A von Keudell

    The excitation and dissociation of CO 2 admixed to argon and helium atmospheric pressure radio frequency plasmas is analyzed. The absorbed plasma power is determined by voltage and current probe measurements and the excitation and dissociation of CO 2 and CO by transmission mode Fourier-transform infrared spectroscopy (FTIR). It is shown, that the vibrational temperatures of CO 2 and CO are significantly higher in an argon compared to a helium plasma. The rotational temperatures remain in both cases close to room temperature. The conversion efficiency, expressed as a critical plasma power to reach almost complete depletion, is four times higher in the argon case. This is explained by the lower threshold for the generation of energetic particles (electrons or metastables) in argon as the main reactive collision partner, promoting excitation and dissociation of CO 2 , by the less efficient quenching of vibrational excited states of CO and CO<...

    更新日期:2020-01-11
  • Electronic structure and hydrogen evolution reaction in Janus monolayer MoSSe regulated by strain engineering
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-10
    Jiaqing Yuan, Yun Shan and Tinghui Li

    Recently, the Janus monolayer with structural symmetry-breaking has been synthesized, which displays many special physical and chemical properties. However, the regulation about its electronic structure as an important application in hydrogen evolution reaction (HER) has not been explored so far. Herein, the H and T phased MoSSe monolayer is considered as model to discuss the contribution of structural deformation to electronic structure and Gibbs free energies, searching for a potential application in HER. The calculations disclose that tensile strain not only efficiently reduces the band gap of MoSSe but also makes the Gibbs free energy of adsorbed hydrogen close to zero. Our calculations provide a new insight into regulating material’s electronic structure and HER performance.

    更新日期:2020-01-11
  • Large perpendicular magnetic anisotropy and tunneling magnetoresistance in thermally stable Mo/FeNiB/MgO magnetic tunnel junctions
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-10
    Jian Su, Gang Li, He Bai, Z Z Zhu, Ying Zhang, S S Kang, T Zhu and J W Cai

    Ferromagnetic metal/oxide heterostructures with tunable perpendicular magnetic anisotropy (PMA) and large tunnel magnetoresistance (TMR) are building blocks of spintronic devices. With unprecedented high performance, the perpendicularly magnetized CoFeB/MgO system has been extensively investigated. Here, we report that Mo/FeNiB/MgO and its inverted structure MgO/FeNiB/Mo show large interfacial PMA with high thermal stability, it ensures spontaneous perpendicular magnetization with effective PMA field of about 5 kOe in Mo/FeNiB(1.2 nm)/MgO and MgO/FeNiB(1.5 nm)/Mo after annealing at 400 °C, comparable to the CoFeB/MgO system. Remarkably, the coercivity of perpendicularly magnetized FeNiB layers in either continuous film or patterned structure of micrometers is smaller than that of the CoFeB counterpart by an order. We have fabricated perpendicular magnetic tunnel junctions with pseudo-spin valve structure Mo/FeNiB/MgO/CoFeB/Mo, which show TMR of 113% at room temperature and 221% ...

    更新日期:2020-01-11
  • Direct observation and simultaneous use of linear and quadratic electro-optical effects
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-10
    Patrick Steglich, Christian Mai, Claus Villringer and Andreas Mai

    We report on the direct observation and simultaneous use of the linear and quadratic electro-optical effect and propose a method by which higher-order susceptibilities of electro-optical materials can be determined. The evaluation is based on the separation of the second- and third-order susceptibilities and the experimental technique uses a slot waveguide ring resonator fabricated in integrated photonic circuit technology, which is embedded by a guest-host polymer system consisting of the azobenzene dye Disperse Red 1 in a poly(methyl methacrylate) matrix as an active electro-optical material. The contribution of both effects on the electro-optical response under the influence of static and time-varying electrical fields is investigated. We show that the quadratic electro-optical effect has a significant influence on the overall electro-optical response even with acentric molecular orientated molecules. Our findings have important implications for developing electro-optical dev...

    更新日期:2020-01-11
  • General and fast patterning of semiconductor nanocrystals by femtosecond laser direct writing
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-10
    Yanan Liu, Zhijun Luo, Changsheng Xie and Zongsong Gan

    Semiconductor nanocrystals have shown remarkable performance in the field of displays, solar cells, and photodetectors. But, a rapid method to produce localized stable nanocrystals remains a challenge, impeding the step toward device miniaturization. Here, we present a general and fast approach, femtosecond laser direct writing, for manufacturing these nanocrystals as well as integrating them into substrates in one step. The high peak power of the femtosecond laser induces a nonlinear absorption of the CatX (Cat = Cd or Pb, X = S, Se or Te) precursor at the focal spot. Once the temperature reaches the nucleation temperature, the CatX nanocrystals form immediately. By moving the displacement platform, arbitrary microscale patterns made of nanoscale crystals are obtained, which shows great potential in high-resolution displays and on-chip light sources.

    更新日期:2020-01-11
  • Actively controlled local drug delivery using conductive polymer-based devices
    Appl. Phys. Lett. (IF 3.521) Pub Date : 2020-01-03
    Christopher A. R. Chapman, Estelle A. Cuttaz, Josef A. Goding, Rylie A. Green

    Localized and actively controlled delivery of drugs presents an opportunity for improving bioavailability, therapeutic efficacy, and long-term treatment of injury or disease. Conductive polymer (CP) based systems present a unique opportunity for using inherent electrochemical and actuating properties to ensure that drugs are delivered or retained using charge controlled mechanisms. A number of CP formats have been explored spanning CP films, composites of CPs with polymeric carriers, and organic electronic ion pumps (OEIPs). Each of these designs can be used to deliver drugs with ionic properties that take advantage of the doping and dedoping characteristics of CPs during electrical pulsing or cycling. However, CP composites that use actuation and OEIPs are emerging technologies that can better address the need for the delivery of a wide range of drugs with varying net charge properties. These systems also allow a high drug loading profile, and with an appropriate configuration, they can use additional electrodes to drive drugs into the tissues. There are also innovative opportunities in the delivery of multiple drug types with varying charge properties that can be individually addressed. The future of CP based drug delivery systems will be strongly influenced by translational challenges including the need for regulatory approvals prior to the use of these novel material platforms in the clinic. Multidisciplinary collaboration will be critical to driving technology development and creating a new paradigm in personalized bioelectronic delivery of therapeutics.

    更新日期:2020-01-10
  • Perspective: Toward highly stable electroluminescent quantum dot light-emitting devices in the visible range
    Appl. Phys. Lett. (IF 3.521) Pub Date : 2020-01-06
    Tyler Davidson-Hall, Hany Aziz

    With significant improvements in external quantum efficiency (EQE) and stability for red, green, and blue devices over the past decade, the future of electroluminescent quantum dot light-emitting devices (QDLEDs) is bright. State-of-the-art QDLEDs have achieved >30% EQE and a >2 000 000 h electroluminescence half-life for an initial luminance of 100 cd m−2, rivaling those of organic light-emitting devices. To date, most of the improvements in QDLED performance have been primarily achieved via advancements in QD synthesis and design that aim at reducing Auger recombination and improving the balance between electron and hole concentrations in the emissive QD layer. However, recent work is starting to reveal the critical role that other device layers, as well as interlayer interfaces, play in limiting QDLED stability. Degradation within the organic hole transport layer (HTL) and near the QD/HTL interface has recently been found to lead to the formation of nonradiative recombination centers that quench excitons in the emissive QD layer and contribute to QDLED failure over time. Looking forward, minimizing degradation in the charge transport layers will likely be crucial for the realization of highly stable QDLEDs and this perspective provides potential avenues to achieve these enhancements. In particular, tailoring the QD energy levels via material selection or interfacial dipoles may reduce charge carrier accumulation in the transport layers and replacing the organic HTL with an inorganic alternative may be an effective approach to circumvent the inherent susceptibility of organic semiconductors to exciton-induced degradation.

    更新日期:2020-01-10
  • Orientation-selective elliptic optical vortex array
    Appl. Phys. Lett. (IF 3.521) Pub Date : 2020-01-02
    Y. K. Wang, H. X. Ma, L. H. Zhu, Y. P. Tai, X. Z. Li

    We propose an orientation-selective elliptic optical vortex array (OS-EOVA). Using multicoordinate (namely, polar, Cartesian, and elliptic) transformations, three kinds of operations applied on optical vortex elements (including location, rotation, and stretching) were executed to obtain the desired orientation in the observed plane. Then, exploiting the reverse design technique, the above-mentioned operations were mapped onto the initial execution plane via Fourier transform. Based on this, 1D and 2D OS-EOVAs were generated experimentally and the existence of optical vortices was verified. Specific OS-EOVAs were designed, possessing antenna array orientation as well as radial and azimuthal orientation. Compared to existing OVAs, the OS-EOVA provides an additional modulated dimension, i.e., orientation. This technique will open up some potential applications, such as complex manipulation of multiparticle systems and fabrication of micromaterials with orientation.

    更新日期:2020-01-10
  • Temperature profile and transient response of thermally tunable ridge waveguides with laterally supported suspension
    Appl. Phys. Lett. (IF 3.521) Pub Date : 2020-01-03
    Fei Duan, Kai Chen, Siyi Wang, Lan Wei, Yonglin Yu, Dayan Ban

    Using the thermoreflectance imaging method, the temperature profile and transient response of thermally tunable ridge waveguides with laterally supported suspension are investigated. This method has a high accuracy in the temperature measurement. The experimental data convincingly confirm a uniform temperature distribution along the waveguide except the initial 30 μm long sections near the two longitudinal edges. The 10%–90% rising time and 90%–10% falling time of the device transient thermal response are also measured to be ∼48 μs and ∼44 μs, respectively, regardless of different waveguide lengths and at different heating powers. In addition, the delay time of the waveguide transient thermal response is revealed to be 1.3 μs by comparison between experiment and simulation.

    更新日期:2020-01-10
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