bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of the suction/injection and external free stream on the instability of a boundary layer over a rotating disk
Authors: Al Saeedi Bashar , Abdelrazik Fathy , Fildes Matthew , Hussain Zahir
Published: May 2023

In this paper, we investigated the effectiveness of the strength of axial flow and suction/injection for the viscous mode (type II) instability within the boundary layer of a rotating disk. To investigate the lower branch, we scaled the viscous mode by using a familiar triple-deck structure analogous to that which was found for Blasius flow over a flat plate. We also analyzed the linear stability behavior of high-Reynolds laminar-turbulent transition. To describe the stationary type II wavenumber and waveangle, we conducted an asymptotic analysis followed by a comparison with the type I mode. We found that a positive axial flow had a stabilizing effect and vice versa a negative axial flow exhibited a destabilizing effect. The results were consistent with previous studies in the literature for positive axial flow, as disturbances were advected downstream in the radial direction. Regarding the suction/injection study, we found suction to be stabilizing, which aligns with previous results in the literature although, conversely, the injection was found to be destabilizing. For the numerical analysis, we found that parameters which result in an increase or decrease of the critical Reynolds number led to a stabilization or destabilization of the flow, respectively. Finally, we compared the asymptotic and numerical stability results for both types I and II followed by the critical Reynolds numbers comparisons, which were found to be consistent in general with results in the literature.
Mapping AC susceptibility with quantum diamond microscope
Authors: Dasika Shishir , Parashar Madhur , Saha Kasturi
Published: May 2023

We present a technique for determining the micro-scale AC susceptibility of magnetic materials. We use the magnetic field sensing properties of nitrogen-vacancy (NV−) centers in diamond to gather quantitative data about the magnetic state of the magnetic material under investigation. A quantum diamond microscope with an integrated lock-in camera is used to perform pixel-by-pixel, lock-in detection of NV− photo-luminescence for high-speed magnetic field imaging. In addition, a secondary sensor is employed to isolate the effect of the excitation field from fields arising from magnetic structures on NV− centers. We demonstrate our experimental technique by measuring the AC susceptibility of soft permalloy micro-magnets at excitation frequencies of up to 20 Hz with a spatial resolution of 1.2 µm and a field of view of 100 µm. Our work paves the way for microscopic measurement of AC susceptibilities of magnetic materials relevant to physical, biological, and material sciences.
A Gaussian field approach to the planar electric double layer structures in electrolyte solutions
Authors: Xiao Tiejun , Song Xueyu
Published: May 2023

In this work, the planar, electric, double-layer structures of non-polarizable electrodes in electrolyte solutions are studied with Gaussian field theory. A response function with two Yukawa functions is used to capture the electrostatic response of the electrolyte solution, from which the modified response function in the planar symmetry is derived analytically. The modified response function is further used to evaluate the induced charge density and the electrostatic potential near an electrode. The Gaussian field theory, combined with a two-Yukawa response function, can reproduce the oscillatory decay behavior of the electric potentials in concentrated electrolyte solutions. When the exact sum rules for the bulk electrolyte solutions and the electric double layers are used as constraints to determine the parameters of the response function, the Gaussian field theory could at least partly capture the nonlinear response effect of the surface charge density. Comparison with results for a planar electrode with fixed surface charge densities from molecular simulations demonstrates the validity of Gaussian field theory.
Implementing microwave impedance microscopy in a dilution refrigerator
Authors: Jiang Zhanzhi , Chong Su Kong , Zhang Peng , Deng Peng , Chu Shizai , Jahanbani Shahin , Wang Kang L. , Lai Keji
Published: May 2023

We report the implementation of a dilution refrigerator-based scanning microwave impedance microscope with a base temperature of ∼100 mK. The vibration noise of our apparatus with tuning-fork feedback control is as low as 1 nm. Using this setup, we have demonstrated the imaging of quantum anomalous Hall states in magnetically (Cr and V) doped (Bi, Sb)2Te3 thin films grown on mica substrates. Both the conductive edge modes and topological phase transitions near the coercive fields of Cr- and V-doped layers are visualized in the field-dependent results. Our study establishes the experimental platform for investigating nanoscale quantum phenomena at ultralow temperatures.
A novel AC flatness adjustment technique for wideband resistive voltage dividers
Authors: Hu Hongjun , Shen Haikuo , Zhao Baoshui
Published: May 2023

Resistive voltage dividers (RVDs) are commonly used as AC attenuation networks in measurement circuits; however, their high-frequency gain is always disturbed by nasty parasitic elements and deviates significantly from the desired design value. This paper proposes a closed-loop adjustment technique for adjusting the frequency response flatness of wideband RVDs (WRVDs). In the proposed adjustment scheme, the frequency response flatness of the WRVD is determined by a voltage-controlled compensation capacitor, whereas the corresponding control voltage is provided by a digital potentiometer. The settling time and the adjustment error of the loop are analyzed to evaluate the adjustment performance. To verify the concept, the adjustment loop is incorporated into a 100:1 WRVD for demonstration. Final experiments show that the proposed technique improves gain flatness by 81 times compared with uncompensated flatness, with 1.15% up to 2 MHz, and that the compensated voltage divider has an excellent linearity of 36 ppm up to 100 V.
Statistical spatial properties of a light field on a target plane
Authors: Xu Shouying , Zhou Shenlei , Tang Yanghui , Fan Wei
Published: May 2023

Studying the light field characteristics of a target plane is critical in controlling the laser-plasma instability (LPI), which is necessary to increase laser energy utilization and compression symmetry in high-power laser facilities. In this study, a statistical method is used to analyze the transmission light characteristics of a target plane for single and multiple beams. We reconstructed the light transmission model on the target plane and analyzed the relationships between the focal spot width and incidence angle, and speckle width and incidence angle using the autocorrelation function. In addition, the relationship between the interference pattern and incident beams is obtained by deriving the beam superposition theory. The results show that the speckle and focal spot widths are stretched in the direction in which the incident plane projects. The direction of the interference structure generated by multiple-laser beams is perpendicular to the line joining of the sub-beams, and the period is related to both wavelength and incidence angle. Experimental results are consistent with the theoretical analysis. The influence of incident beam number on the focal spot uniformity is also studied. The results are of great significance for regulating the sub-beam incidence direction, understanding light properties to further improve focal spot uniformity and suppress the LPI.
Theoretical insight on the charge transport properties: The formation of “head-to-tail” and “head-to-head” stacking of asymmetric aryl anthracene derivatives
Authors: Sun Xiao-Qi , Qin Gui-Ya , Li Hui-Yuan , Jin Heng-Yu , Wang Rui , Li Hui , Ren Ai-Min , Guo Jing-Fu
Published: May 2023

Organic semiconductors (OSCs) are widely used in flexible display, renewable energy, and biosensors, owing to their unique solid-state physical and optoelectronic properties. Among the abundant crystal library of OSCs, asymmetric aryl anthracene derivatives have irreplaceable advantages due to the interplay between their distinct π-conjugated geometry and molecular stacking as well as efficient light emission and charge transport properties that can be simultaneously utilized. However, the poor crystal stacking patterns of most asymmetric molecules limit their utility as excellent OSCs. Thus, it is crucial to clarify the structural features that enable the extremely ordered stacking and favorable electronic structure of asymmetric anthracene derivatives to become high-performance OSCs. This contribution investigates the charge transport properties of a series of asymmetric aryl anthracene derivatives to reveal the modulation factors of the molecular stacking modes and to explore the structural factors, which are beneficial to charge transport. The analysis demonstrated that the vinyl-linker facilitated the injection of hole carriers, and the alkynyl-linker effectively reduces the reorganization energy. Importantly, the linear polarizability and permanent dipole moment of a single molecule play a vital regulation to molecular stacking modes and the transfer integral of the dimer. The “head-to-head stacking” motif shows a compact stacking pattern and the maximum 2D anisotropic mobility more than 10 cm2 V−1 s−1. These findings sharpen our understanding of the charge transport properties in asymmetric organic semiconductors and are essential for developing a diverse range of high-performance OSC materials.
Influence of high pressure on the remarkable itinerant electron behavior in Y0.7Er0.3Fe2D4.2 compound
Authors: Arnold Z. , Isnard O. , Paul-Boncour V.
Published: May 2023

A monoclinic Y0.7Er0.3Fe2D4.2 compound exhibits unusual magnetic properties with different field induced magnetic transitions. The deuteride is ferrimagnetic at low temperature, and the Er and Fe sublattices present magnetic transitions at different temperatures. The Er moments are ordered below TEr = 55 K, whereas the Fe moments remain ferromagnetically coupled up to TM0 = 66 K. At TM0, the Fe moments display a sharp ferromagnetic–antiferromagnetic transition (FM–AFM) through itinerant electron metamagnetic behavior very sensitive to any volume change. Y0.7Er0.3Fe2D4.2 becomes paramagnetic above TN = 125 K. The pressure dependence of TEr and TM0 has been extracted from magnetic measurements under hydrostatic pressure up to 0.49 GPa. Both temperatures decrease linearly upon applied pressure with dTEr/dP = −126 and dTM0/dP = −140 K GPa−1 for a field of B = 0.03 T. Both magnetic Er and ferromagnetic Fe orders disappear at P = 0.44(4) GPa. However, under a larger applied field B = 5 T, dTM0/dP = −156 K GPa−1, whereas dTEr/dP = −134 K GPa−1 showing weaker sensitivity to pressure and magnetic field. At 2 K, the decrease of the saturation magnetization under pressure can be attributed to a reduction of the mean Er moment due to canting and/or a crystal field effect. Above TM0, the magnetization curves display metamagnetic behavior from an AFM to FM state, which is also very sensitive to the applied pressure. The transition field Btrans, which increases linearly upon heating, is shifted to a lower temperature upon applied pressure with ΔT = −17 K between 0 and 0.11 GPa. These results show strong decoupling of the Er and Fe magnetic sublattices vs temperature, applied field, and pressure.
Kinetic inductance of superconducting nanostrips with turns
Authors: Mawatari Yasunori
Published: May 2023

Kinetic inductances of superconducting nanostrips with a meander pattern are theoretically investigated based on the London model, and the effect of the current crowding at the turns of the nanostrips is considered. The complex current approach is developed for analytical investigation of the kinetic inductance of nanostrips with turns for thin d<λ and narrow w≪λ2/d superconducting strips, where d is the strip thickness, w is the strip width, and λ is the London penetration depth. We show that the current distribution in superconducting nanostrips of wd≪λ2 is identical to that in normal conducting nanostrips of wd≪δ2/2, where δ is the skin depth, and the dependence of the kinetic inductance on the nanostrip geometry is identical to that of the normal resistance. Effects of the edge defects of superconducting strips upon the kinetic inductance are also considered.
Predicting complex multicomponent particle–liquid flow in a mechanically agitated vessel via machine learning
Authors: Li Kun , Savari Chiya , Barigou Mostafa
Published: May 2023

Machine learning (ML) is used to build a new computationally efficient data-driven dynamical model for single-phase and complex multicomponent particle–liquid turbulent flows in a stirred vessel. By feeding short-term trajectories of flow phases or components acquired experimentally for a given flow condition via a positron emission particle tracking (PEPT) technique, the ML model learns primary flow dynamics from the input driver data and predicts new long-term trajectories pertaining to new flow conditions. The model performance is evaluated over a wide range of flow conditions by comparing ML-predicted flow fields with extensive long-term experimental PEPT data. The ML model predicts the local velocities and spatial distribution of each flow phase and component to a high degree of accuracy, including conditions of impeller speeds, particle loadings and sizes within and without the range of the input driver datasets. A new flow analysis and modeling strategy is thus developed, whereby only short-term experiments (or alternatively high-fidelity simulations) covering a few typical flow situations are sufficient to enable the prediction of complex multiphase flows, significantly reducing experimental and/or simulation costs.
NiO junction termination extension for high-voltage (>3 kV) Ga2O3 devices
Authors: Xiao Ming , Wang Boyan , Spencer Joseph , Qin Yuan , Porter Matthew , Ma Yunwei , Wang Yifan , Sasaki Kohei , Tadjer Marko , Zhang Yuhao
Published: May 2023

Edge termination is the enabling building block of power devices to exploit the high breakdown field of wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductors. This work presents a heterogeneous junction termination extension (JTE) based on p-type nickel oxide (NiO) for gallium oxide (Ga2O3) devices. Distinct from prior JTEs usually made by implantation or etch, this NiO JTE is deposited on the surface of Ga2O3 by magnetron sputtering. The JTE consists of multiple NiO layers with various lengths to allow for a graded decrease in effective charge density away from the device active region. Moreover, this surface JTE has broad design window and process latitude, and its efficiency is drift-layer agnostic. The physics of this NiO JTE is validated by experimental applications into NiO/Ga2O3 p–n diodes fabricated on two Ga2O3 wafers with different doping concentrations. The JTE enables a breakdown voltage over 3.2 kV and a consistent parallel-plate junction field of 4.2 MV/cm in both devices, rendering a power figure of merit of 2.5–2.7 GW/cm2. These results show the great promise of the deposited JTE as a flexible, near ideal edge termination for WBG and UWBG devices, particularly those lacking high-quality homojunctions.
Micro-thermography for imaging ice crystal growth and nucleation inside non-transparent materials
Authors: Zalazar Martin , Zypman Fredy , Drori Ran
Published: May 2023

Ice crystal growth and nucleation rate measurements are usually done using light microscopy in liquid and transparent samples. Yet, the understanding of important practical problems depends on monitoring ice growth inside solid materials, for example how rapid ice growth leads to structural damage of food, or how the final structure of cementitious materials is affected by ice during curing. Imaging crystal growth inside solid materials cannot be done with visible light and is intrinsically more challenging than visible light imaging. Thermography is a technique that uses thermal (infrared) cameras to monitor temperature changes in a material, and it has been used to provide a qualitative description of ice propagation with a low spatial resolution. Here, we describe a method that uses a novel micro-thermography system to image ice nucleation and growth inside non-transparent samples. This method relies on two major components: a cold stage with accurate temperature control (±0.001 °C) and a thermal camera with high spatial and temperature resolution. Our experiments include imaging of ice formation and growth in pure water first and then inside plant leaves used as a model for a non-transparent material. An ice growth rate of 2.2 mm/s was measured inside a plant leaf at −12 °C, and ice nucleation in single plant cells was observed as a hotspot having a diameter of 160 µm. The results presented here provide an experimental proof that high-quality imaging of ice growth is achievable, thus paving the way for quantitative measurements of ice growth kinetics and ice nucleation in solid materials.
Size-dependent errors in real-time electron density propagation
Authors: Ranka Karnamohit , Isborn Christine M.
Published: May 2023

Real-time (RT) electron density propagation with time-dependent density functional theory (TDDFT) or Hartree–Fock (TDHF) is one of the most popular methods to model the charge transfer in molecules and materials. However, both RT-TDHF and RT-TDDFT within the adiabatic approximation are known to produce inaccurate evolution of the electron density away from the ground state in model systems, leading to large errors in charge transfer and erroneous shifting of peaks in absorption spectra. Given the poor performance of these methods with small model systems and the widespread use of the methods with larger molecular and material systems, here we bridge the gap in our understanding of these methods and examine the size-dependence of errors in RT density propagation. We analyze the performance of RT density propagation for systems of increasing size during the application of a continuous resonant field to induce Rabi-like oscillations, during charge-transfer dynamics, and for peak shifting in simulated absorption spectra. We find that the errors in the electron dynamics are indeed size dependent for these phenomena, with the largest system producing the results most aligned with those expected from linear response theory. The results suggest that although the RT-TDHF and RT-TDDFT methods may produce severe errors for model systems, the errors in charge transfer and resonantly driven electron dynamics may be much less significant for more realistic, large-scale molecules and materials.
Dubrovin–Frobenius manifolds associated with Bn and the constrained KP hierarchy
Authors: Ma Shilin , Zuo Dafeng
Published: May 2023

In this paper, we will show that the Dubrovin–Frobenius prepotentials on the orbit space of the Coxeter group Bn constructed by Arsie et al. [Sel. Math. New Ser. 29, 1 (2023)] coincide with the solutions of Witten-Dijkgraaf-Verlinde-Verlinde (WDVV) equations associated with the constrained KP hierarchy.
Lead indium niobate-lead magnesium niobate-lead titanate based whispering gallery mode resonator
Authors: Zhuang Yongyong , Zhang Yifan , Yang Liu , Yu Jianhui , Guo Haisheng , Song Kexin , Hu Qingyuan , Yang Lihong , Zhang Hao , Wei Xiaoyong , Xu Zhuo
Published: May 2023

Whispering gallery mode resonators (WGMRs) have garnered significant interest due to their potential applications in the fields of electro-optic modulation and microwave to optical photon conversion. In this study, we have leveraged an electro-optic crystal, lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT), to fabricate a high-quality WGMR. Our investigation revealed that the crystal composition used in this work is 0.24PIN-0.45PMN-0.31PT, and each element of the whole sample is homogeneously distributed. The dielectric properties of the sample revealed the necessity of limiting the temperature and external electric field frequency to below 100 °C and 106 Hz, respectively. The obtained optical quality factor value (Q value) of the resonator is ∼0.7 × 105. Impressively, our resonator could be conveniently tuned by exploiting the enormous inverse piezoelectric effect d31 of the crystal, thereby alleviating the need for precise fabrication. Furthermore, a theoretical analysis of our resonator revealed that a calculated resonance wavelength shift is within a broad range of 2.16 nm. Intriguingly, if the surface roughness of the resonator is reduced tenfold, we can increase the calculated Q value dependent on surface scattering by 104. Our finding showcases the tremendous potential of the PIN-PMN-PT crystal-based WGMR as versatile building blocks for a variety of applications in the burgeoning field of photonic technology.
Simultaneous measurement of specific heat and thermal conductivity in pulsed magnetic fields
Authors: Nomoto Tetsuya , Zhong Chengchao , Kageyama Hiroshi , Suzuki Yoko , Jaime Marcelo , Hashimoto Yoshiaki , Katsumoto Shingo , Matsuyama Naofumi , Dong Chao , Matsuo Akira , Kindo Koichi , Izawa Koichi , Kohama Yoshimitsu
Published: May 2023

We report an experimental setup for simultaneously measuring specific heat and thermal conductivity in feedback-controlled pulsed magnetic fields of 50 ms duration at cryogenic temperatures. A stabilized magnetic field pulse obtained by the feedback control, which dramatically improves the thermal stability of the setup and sample, is used in combination with the flash method to obtain absolute values of thermal properties up to 37.2 T in the 22–16 K temperature range. We describe the experimental setup and demonstrate the performance of the present method with measurements on single-crystal samples of the geometrically frustrated quantum spin-dimer system SrCu2(BO3)2. Our proof-of-principle results show excellent agreement with data taken using a standard steady-state method, confirming the validity and convenience of the present approach.
Study of turbulent transport in magnetized plasmas with flow using symplectic maps
Authors: Torres Jorge , Martinell Julio J.
Published: May 2023

Turbulent transport in a magnetized plasma of the kind found in tokamaks is modeled by a 2D wave spectrum that allows reduction to a symplectic map. The properties of particle transport when chaos sets in are analyzed in various circumstances including finite Larmor radius (FLR) effects and a background plasma flow. For large wave amplitudes, regular particle orbits become chaotic, which represents a type of Lagrangian turbulence. When chaos becomes global, it leads to the loss of particle confinement. Poloidal flows tend to decrease the chaos in some regions, and they can give rise to the formation of transport barriers. FLR effects not only reduce chaos but also give rise to non-local behavior. Thus, when the particles have a thermal distribution of Larmor radii, a non-Gaussian particle distribution function in space is obtained. However, the transport preserves its diffusive scaling when there is no flow. Previous results about the dependence of the diffusion coefficient with amplitude are re-derived analytically and numerically taking into account FLR effects. In the presence of general poloidal flows, the transport has to be described by a two-step map. They modify the nature of transport in the direction of the flow from diffusive to ballistic to super-ballistic, depending on the type of flow. The transverse transport, in turn, shows suppression of the oscillations with wave amplitude that are present in the absence of flow. When the plasma flow varies linearly with radius, the transport can be studied with a similar single-step map, and the transverse diffusion coefficient is reduced while parallel transport can become super-ballistic. For non-monotonic flows, there are accelerating modes that can produce ballistic-like particles while the bulk of the particles behaves diffusively.
Electron hopping heat transport in molecules
Authors: Craven Galen T. , Nitzan Abraham
Published: May 2023

The realization of single-molecule thermal conductance measurements has driven the need for theoretical tools to describe conduction processes that occur over atomistic length scales. In macroscale systems, the principle that is typically used to understand thermal conductivity is Fourier’s law. At molecular length scales, however, deviations from Fourier’s law are common in part because microscale thermal transport properties typically depend on the complex interplay between multiple heat conduction mechanisms. Here, the thermal transport properties that arise from electron transfer across a thermal gradient in a molecular conduction junction are examined theoretically. We illustrate how transport in a model junction is affected by varying the electronic structure and length of the molecular bridge in the junction as well as the strength of the coupling between the bridge and its surrounding environment. Three findings are of note: First, the transport properties can vary significantly depending on the characteristics of the molecular bridge and its environment; second, the system’s thermal conductance commonly deviates from Fourier’s law; and third, in properly engineered systems, the magnitude of electron hopping thermal conductance is similar to what has been measured in single-molecule devices.
Terahertz generation through optical rectification in reflection
Authors: Hedegaard Kristensen Mathias , Herault Emilie , Zhai Dongwei , Skovsen Esben , Coutaz Jean-Louis
Published: May 2023

In this paper, we study terahertz generation through optical rectification in reflection at normal incidence in a dielectric nonlinear crystal. We first analyze, with a nonlinear optical model, the sample parameters (thickness, absorption at both laser and terahertz wavelengths, etc.) for which a terahertz optical rectification reflection scheme is preferable to the common transmission scheme. Then, we report our experimental observations of a reflected terahertz signal generated at the surface of a ZnTe crystal. The reflected terahertz signal shares all the characteristics of a signal generated in transmission but is not limited by absorption losses in the crystal, thereby providing a broader bandwidth. At high pump laser power, the signal exhibits saturation, which is caused by the decrease of the nonlinear susceptibility due to photocarriers generated by two-photon absorption. This reflection scheme could be of great importance for terahertz microscopy of opaque materials like, e.g., humid samples or samples exhibiting strong absorption bands or to study samples for which the transmitted signal cannot be recorded.
Influence of intrinsic amorphous silicon passivation layer on the dark-state stability of SHJ cells
Authors: Zhang Honghua , Zhang Liping , Liu Wenzhu , Zhou Yinuo , Lan Shihu , Jiang Kai , Du Junlin , Han Anjun , Zhao Hui , Zhang Haichuan , Shi Jianhua , Meng Fanying , Liu Zhengxin
Published: May 2023

Silicon heterojunction (SHJ) solar cells with a two-densities stacked intrinsic hydrogenated amorphous silicon (i-a-Si:H) thin film passivated crystalline silicon surface have high VOC and efficiency. We investigated the dark stability of cells varied with the microstructure of i-a-Si:H layers. It has been found that the dark degradation is mainly from the change in the silicon hydrogen bonded configuration associated with voids size. Furthermore, the less degradation exists on cells with thicker dense i-a-Si:H layers, which results from the high bonded hydrogen content after the enhanced light-soaking (LS) and less change in voids during the dark storage in the i-a-Si:H layers. The microstructure changes, including bonded hydrogen content, voids size, and voids quantity, are related to the initial microstructure of i-a-Si:H layers. This can be illustrated by two actions of non-bonded hydrogens immersed in the undense part of the silicon network. As a result, to enhance the bonded hydrogen content in the i-a-Si:H layers is a preferred method to improve the dark stability of SHJ solar cell after LS.
Composite nanoparticle-metal-organic frameworks for SERS sensing
Authors: Zorlu Tolga , Correa-Duarte Miguel A. , Alvarez-Puebla Ramon A.
Published: May 2023

In recent years, metal-organic frameworks, in general, and zeolitic imidazolate frameworks, in special, had become popular due to their large surface area, pore homogeneity, and easy preparation and integration with plasmonic nanoparticles to produce optical sensors. Herein, we summarize the late advances in the use of these hybrid composites in the field of surface-enhanced Raman scattering and their future perspectives.
Strong collisionless coupling between an unmagnetized driver plasma and a magnetized background plasma
Authors: Cruz F. D. , Schaeffer D. B. , Cruz F. , Silva L. O.
Published: May 2023

Fast-exploding plasmas traveling though magnetized, collisionless plasmas can occur in a variety of physical systems, such as supernova remnants, coronal mass ejections, and laser-driven laboratory experiments. To study these systems, it is important to understand the coupling process between the plasmas. In this work, we develop a semi-analytical model of the parameters that characterize the strong collisionless coupling between an unmagnetized driver plasma and a uniformly and perpendicularly magnetized background plasma. In particular, we derive analytical expressions that describe the characteristic diamagnetic cavity and magnetic compression of these systems, such as their corresponding velocities, the compression ratio, and the maximum size of the cavity. The semi-analytical model is compared with collisionless 1D particle-in-cell simulations and experimental results with laser-driven plasmas. The model allows us to provide bounds for parameters that are otherwise difficult to diagnose in experiments with similar setups.
Single-flux-quantum signal processors monolithically integrated with a superconducting nanostrip single-photon detector array
Authors: Miyajima Shigeyuki , Yabuno Masahiro , Miki Shigehito , Nagasawa Shuichi , Hidaka Mutsuo , Terai Hirotaka
Published: May 2023

We developed a monolithic integration process for a superconducting nanostrip single-photon detector (SNSPD) and a cryogenic signal processor based on a single-flux-quantum (SFQ) circuit. Sixteen-pixel SNSPDs consisting of a 10-nm-thick and 100-nm-wide NbTiN nanowire were fabricated on a 3-in. Si wafer with an SFQ merger fabricated by the National Institute of Advanced Industrial Science and Technology Nb 2.5 kA/cm2 standard process 2. Subsequently, we illuminated the photons on the 16-pixel SNSPD array through an optical fiber and obtained a similar bias-current dependence of the detection efficiency with a single-pixel SNSPD without the SFQ merger. This indicates that the SFQ merger works correctly, and that the power dissipation of the SFQ circuit, which is estimated to be 200 μW, does not deteriorate the photon detection of SNSPD fabricated on the same chip with a size of 5 × 5 mm2. Furthermore, we measured timing jitter using a pulsed laser as the photon source. Owing to the careful tuning of the wiring length between each pixel of the 16-pixel SNSPD and each input port of the SFQ merger, the obtained timing jitter was 41.4 ps, which is approximately equal to or less than that of the single-pixel SNSPD.
Magnetostatic ponderomotive potential in rotating plasma
Authors: Rubin T. , Rax J. M. , Fisch N. J.
Published: May 2023

A new end-plugging method for rotating plasmas is identified and analyzed. It uses the ponderomotive potential associated with an azimuthal magnetostatic wiggler. Studied both analytically and numerically, this process compares favorably to other end-plugging methods in open field line magnetized plasma devices.
E–H transitions in Ar/O2 and Ar/Cl2 inductively coupled plasmas: Antenna geometry and operating conditions
Authors: Piskin Tugba , Qian Yuchen , Pribyl Patrick , Gekelman Walter , Kushner Mark J.
Published: May 2023

Electronegative inductively coupled plasmas (ICPs) are used for conductor etching in the microelectronics industry for semiconductor fabrication. Pulsing of the antenna power and bias voltages provides additional control for optimizing plasma–surface interactions. However, pulsed ICPs are susceptible to capacitive-to-inductive mode transitions at the onset of the power pulse due to there being low electron densities at the end of the prior afterglow. The capacitive (E) to inductive (H) mode transition is sensitive to the spatial configuration of the plasma at the end of the prior afterglow, circuit (matchbox) settings, operating conditions, and reactor configurations, including antenna geometry. In this paper, we discuss results from a computational investigation of E–H transitions in pulsed ICPs sustained in Ar/Cl2 and Ar/O2 gas mixtures while varying operating conditions, including gas mixture, pulse repetition frequency, duty cycle of the power pulse, and antenna geometry. Pulsed ICPs sustained in Ar/Cl2 mixtures are prone to significant E–H transitions due to thermal dissociative attachment reactions with Cl2 during the afterglow which reduce pre-pulse electron densities. These abrupt E–H transitions launch electrostatic waves from the formation of a sheath at the boundaries of the plasma and under the antenna in particular. The smoother E–H transitions observed for Ar/O2 mixture results from the higher electron density at the start of the power pulse due to the lack of thermal electron attaching reactions to O2. Ion energy and angular distributions (IEADs) incident onto the wafer and the dielectric window under the antenna are discussed. The shape of the antenna influences the severity of the E–H transition and the IEADs, with antennas having larger surface areas facing the plasma producing larger capacitive coupling. Validation of the model is performed by comparison of computed electron densities with experimental measurements.
Concomitant modulation of interlayer exchange coupling and Gilbert damping in Fe/CoO with spin conductor Ag layer at interface
Authors: He J. , Zhao Z. R. , Xia H. , Li T. , Liang E. , Ni G. , Wang J. , Sheng C. X. , Chen L. Y. , Wu Y. Z. , Zhao H. B.
Published: May 2023

We report on the modulation of interlayer exchange coupling (IEC) between the ferromagnet (FM) Fe and insulating antiferromagnet (AFM) CoO and its impact on the Gilbert damping by a time-resolved magneto-optical Kerr effect technique. By inserting a wedge spin conductor Ag layer at the interface of Fe/CoO, it is revealed that both uniform spin precession frequency and Gilbert damping constant of Fe film decrease with increasing Ag thickness up to ∼2 nm, and above that with eliminated IEC, these two parameters reach the intrinsic values of the Fe film. The precession frequency and damping also show similar variation tendency with temperature for attenuated IEC. These results prove that the exchange coupling at the FM–AFM interface plays an essential role for the spin angular momentum transfer to the insulating AFM layer, and the spin pumping is insignificant even for the very thin spin conductor layer. Our findings may have general insights into the role of the FM/AFM interface in the magnetization dynamics and spin angular momentum transfer for future spintronic applications.
Improper ferroelectricity in ultrathin hexagonal ferrites films
Authors: Li Xin , Yun Yu , Xu Xiaoshan
Published: May 2023

Suppression of ferroelectricity in ultrathin films of improper ferroelectric hexagonal ferrites or manganites has been attributed to the effect of interfacial clamping; however, the quantitative understanding and related phenomenological model are still lacking. In this work, we report on the paraelectric-to-ferroelectric phase transition of epitaxial h-ScFeO3 films with different thicknesses through in situ reflection high-energy electron diffraction. Based on the interfacial clamping model and the Landau theory, we show that the thickness-dependence of the ferroelectric Curie temperature can be understood in terms of the characteristic length of an interfacial clamping layer and the bulk Curie temperature. Furthermore, we found that the critical thickness of improper ferroelectricity is proportional to the characteristic length of the interfacial clamping layer. These results reveal the essential role of mechanical clamping from interface on the improper ferroelectricity of hexagonal ferrites or manganites and could serve as the guidance to achieve robust improper ferroelectricity in ultrathin films.
A flux-tunable YBa2Cu3O7 quantum interference microwave circuit
Authors: Uhl Kevin , Hackenbeck Daniel , Füger Christoph , Kleiner Reinhold , Koelle Dieter , Bothner Daniel
Published: May 2023

Josephson microwave circuits are essential for the currently flourishing research on superconducting technologies, such as quantum computation, quantum sensing, and microwave signal processing. To increase the possible parameter space for device operation with respect to the current standards, many materials for superconducting circuits are under active investigation. Here, we present the realization of a frequency-tunable, weakly nonlinear Josephson microwave circuit made of the high-temperature cuprate superconductor YBa2Cu3O7 (YBCO), a material with a high critical temperature and a very high critical magnetic field. An in situ frequency-tunability of ∼300 MHz is achieved by integrating a superconducting quantum interference device (SQUID) into the circuit based on Josephson junctions directly written with a helium ion microscope (HIM). Our results demonstrate that YBCO-HIM-SQUID microwave resonators are promising candidates for quantum sensing and microwave technology applications.
A thorough study on the electrical performance change and trap evolution of AlGaN/GaN MIS-HEMTs under proton irradiation
Authors: Zhu Tian , Zheng Xue-Feng , Yin Tai-Xu , Zhang Hao , Wang Xiao-Hu , Yue Shao-Zhong , Wang Tan , Han Tao , Ma Xiao-Hua , Hao Yue
Published: May 2023

In this work, the effects of proton-induced trap evolution on the electrical performances of AlGaN/GaN metal–insulator–semiconductor (MIS) high-electron-mobility-transistors (HEMTs) have been investigated in detail. Contrary to observed proton-induced degradation in sheet electron density (ns), carrier mobility (μn), and sheet resistance (RSH), a significant improvement in gate leakage current (IG) and off-state drain–source breakdown voltage (BVDS) is found in irradiated devices. The low-frequency noise (LFN) results show that the density of traps in the AlGaN layer and AlGaN/GaN interface increases after irradiation, which leads to a degradation in ns, μn, and RSH and an improvement in BVDS due to enhanced electron trapping and depletion. Furthermore, the measurement results obtained from the frequency-dependent conductance technique show that irradiated devices exhibit decreased trap density (DT) at the insulator/semiconductor interface with hardly changed trap energy level (ET), which confirms the observed proton-induced decrease in IG. An increase in DT at the AlGaN/GaN interface is also found after irradiation, which is consistent with LFN results. These traps with deeper ET induce a serious Coulomb scattering effect. This work provides valuable information for the systematic understanding of the proton irradiation effect of AlGaN/GaN MIS-HEMTs.
A novel energy harvester based on dual vibrating mechanisms with self-actuation
Authors: Hou Yi , He Lipeng , Liu Xuejin , Wang Shuangjian , Tian Xiaochao , Yu Baojun , Cheng Guangming
Published: May 2023

This paper introduced a novel energy harvester with a tunnel and drop-shaped bluffbody for self-actuation and wind speed sensing. The harvester exhibits dual vibrating mechanisms of vortex-induced vibration (VIV) and galloping. Theoretical and numerical analyses were conducted to study the energy conversion relationship and fluid field of the harvester, and the conclusions were verified by controlled variable experiments. The optimal design values of inlet angle I 40°, polyvinylidene fluoride (PVDF) angle P 10°, and exit angle E 10° were demonstrated with the highest output of 10.42 Vp-p at the wind speed of 18 m/s. The output voltage of the PVDF energy harvester has a reliable relationship with the wind speed as a function of wind speed sensor, which could be applied for meteorological information collection and fluid flow rate monitoring with further study conducted underwater.
Two-stream instability with a growth rate insensitive to collisions in a dissipative plasma jet
Authors: Zhou Yi , Bellan Paul M.
Published: May 2023

The two-stream instability (Buneman instability) is traditionally derived as a collisionless instability with the presumption that collisions inhibit this instability. We show here via a combination of a collisional two-fluid model and associated experimental observations made in the Caltech plasma jet experiment, that in fact, a low-frequency mode of the two-stream instability is indifferent to collisions. Despite the collision frequency greatly exceeding the growth rate of the instability, the instability can still cause an exponential growth of electron velocity and a rapid depletion of particle density. Nevertheless, high collisionality has an important effect as it enables the development of a double layer when the cross section of the plasma jet is constricted by a kink-instigated Rayleigh–Taylor instability.
Inferring electrospray emission characteristics from molecular dynamics and simulated retarding potential analysis
Authors: Schroeder Madeleine , Gallud Ximo , Petro Elaine , Jia-Richards Oliver , Lozano Paulo C.
Published: May 2023

In this work, we present coordinated molecular dynamics, ion cluster acceleration, and retarding potential analysis simulations to determine cluster fragmentation behavior in a realistic emitter geometry for electrosprays operating in the pure ionic regime. Molecular dynamics simulations are used to determine the fragmentation rates of ionic liquid clusters as a function of internal energy, electric field strength, and cluster size. A simplified model of electrospray cluster acceleration is developed from previous electrohydrodynamic emission models and used to simulate retarding potential analysis curves. Fragmentation rates and beam composition are inferred for experimental data based on the molecular dynamics and cluster acceleration simulations. We find that for these experimental data, temperatures of EMI-BF4 dimers likely range between 590 and 687 K while trimer temperatures are larger between 989 and 1092 K. The percentage of monomers, dimers, and trimers in the beam is approximately 45%, 30%–43%, and 13%–25%, respectively. Both ionic liquid cluster temperatures and beam composition agree with previous analysis of this experimental work, supporting the use of coordinated molecular dynamics and retarding potential analysis as a method of inferring electrospray beam parameters. Insights gained from this simulation process are discussed in the context of currently unexplained electrospray emitter behavior and experimental results including the presence of tetramers and trimers in the beam and fragmentation rates in high electric field regions.
Bound states in the continuum (BIC) in silicon nanodisk array on mirror structure: Perfect absorption associated with quasi-BIC below the bandgap
Authors: Moriasa Keisuke , Hasebe Hiroaki , Sugimoto Hiroshi , Fujii Minoru
Published: May 2023

A structure composed of a hexagonal array of Si nanodisks having toroidal dipole resonances and a reflecting mirror separated by a SiO2 spacer is proposed as a platform that exhibits narrow-band perfect absorption in the Si sub-bandgap wavelength range for a CMOS compatible Si based photodetector operating below the bandgap range. The numerical simulation reveals that the structure possesses Fabry–Pérot bound states in the continuum at proper spacer thicknesses due to the interference between the toroidal dipole and its image dipole. By slightly detuning the spacer thickness to meet the critical coupling condition, narrow-band perfect absorption appears despite assumption of a very small extinction coefficient (5 × 10−4). The wavelength of the perfect absorption is controlled in a wide range by the structural parameters of a Si nanodisk hexagonal array and is insensitive to the fluctuation of the extinction coefficient and the choice of a metallic mirror. In the structure, over 90% of incident power can be absorbed in the Si region. This suggests that the structure can be used as a narrow-band photodetector operating in the Si sub-bandgap wavelength range. We also evaluate the sensing performance of the proposed structure as an intensity based refractive index sensor operating in the near-infrared range.
Photoelectric and pyroelectric performance modulated by the in-plane ferroelectric polarization in multi-functional α-In2Se3-based transistor
Authors: Cai Chuanyang , Peng Jie , Ling Shiyu , Hou Pengfei
Published: May 2023

As a typical two-dimensional van der Waals ferroelectric material, α-In2Se3 has great potential in the applications of optoelectronic devices, memories, sensors, detectors, and synapses. Although it has been proved that α-In2Se3 is with simultaneous intercorrelated in-plane and out-of-plane ferroelectric polarization, the degree-of-freedom of in-plane ferroelectric polarization in the α-In2Se3 and its influence on the other properties have always been neglected because of the difficulties in the characterization and application, comparing with the out-of-plane ferroelectric polarization. Specifically, it has not been revealed the influence mechanism how the in-plane ferroelectric polarization modifies the photodetection performance of the α-In2Se3-based transistor. In this report, the four-terminal transistors based on the multi-layered α-In2Se3 are prepared and used to investigate the in-plane ferroelectric polarization influenced photodetection performance. We have demonstrated that the in-plane ferroelectric polarization may reduce the optical response time of α-In2Se3-based transistors, and the pyroelectric performance induced by the in-plane ferroelectric polarization adds a feature to the α-In2Se3-based transistors. These results promote the four-terminal α-In2Se3-based transistor to be a multi-functional device, which can simultaneously detect the light and its induced temperature variation. Our work may offer an approach to understand the in-plane ferroelectric polarization-modulated multi-functional optoelectronics.
Investigation of the formation and evolution of over-tip shock waves in the pressure-driven tip leakage flow by time-resolved schlieren visualization
Authors: Avital Eldad J. , Saleh Zainab J. , Motallebi Fariborz
Published: May 2023

Time-resolved schlieren visualization and transonic wind tunnel are used to investigate tip leakage flows (TLFs) over several generic blade tip models. Focus is on the generation and evolution of the over-tip shock waves in the clearance region. A multi-cutoff superposition technique is developed to improve the schlieren system for better visualization. Unsteady flow structures, such as over-tip shock oscillation, shear-layer flapping, and vortex shedding, are revealed by Fourier analysis and dynamic mode decomposition. To predict the generation and decaying of over-tip shocks, a simplified model is proposed by analogizing the shock system to be an N-shaped sawtooth wave. The results show that (1) the proposed model is able to capture the main features of the generation and decaying of over-tip shock waves. The processes of shock generation, decaying, and fading-out are dominated by the mean background flow, the shock state, and the flow fluctuations, respectively. Adding extra coming flow fluctuations can be an efficient way to control the evolution of over-tip shock system. (2) The shock-oscillating frequency is kept the same with the shear-layer flapping, and shock waves with a given oscillating frequency range is constrained to a specific position range. This is termed the “lock-in effect,” which is also observed in TLFs over contoured blade tips. The non-uniformity generation and the nonlinear propagation of shock waves are responsible for this effect. Constrained by this effect, the evolution of over-tip shock waves is separated into four discrete phases. Thus, this effect can be applied for the control of TLFs.