Showing 1–49 of 49 results for author: Zhong, S

Solving the inverse problem of X-ray absorption spectroscopy via physics-informed deep learning

Authors: Suyang Zhong, Boying Huang, Pengwei Xu, Fanjie Xu, Yuhao Zhao, Jun Cheng, Fujie Tang, Weinan E, Zhong-Qun Tian

Abstract: Resolving transient atomic configurations in non-crystalline or dynamic environments remains a fundamental bottleneck in the physical sciences. While X-ray absorption spectroscopy (XAS) is a premier probe of local structure, inverting spectra into structural descriptors is a notoriously ill-posed problem due to inherent many-to-one mapping. Here, we present the Spectral Pattern Translator (SPT), a… ▽ More Resolving transient atomic configurations in non-crystalline or dynamic environments remains a fundamental bottleneck in the physical sciences. While X-ray absorption spectroscopy (XAS) is a premier probe of local structure, inverting spectra into structural descriptors is a notoriously ill-posed problem due to inherent many-to-one mapping. Here, we present the Spectral Pattern Translator (SPT), a physics-informed deep learning framework that establishes a robust bridge between large-scale theoretical datasets and experimental reality. Our strategy exploits the Fourier duality between spectral energy oscillations and spatial scattering paths to overcome the "simulation-to-experiment" gap. By decomposing spectra into frequency domains, SPT effectively isolates robust structural coordination signals from the destabilizing noise inherent in experimental data. Trained on a massive library of diverse atomic environments, this approach achieves state-of-the-art accuracy in resolving continuous phase transitions in battery cathodes and deciphering local order in amorphous materials. With millisecond-scale latency, SPT removes the primary computational barrier to autonomous materials discovery, establishing a robust, noise-resilient engine for closed-loop robotic chemistry. △ Less

Submitted 29 March, 2026; originally announced March 2026.

Comments: 31 pages, 8 figures

Signatures of Damping Nonlinear Oscillations by KHI-induced Turbulence in Synthetic Observations

Authors: Sihui Zhong, Andrew Hillier, Iñigo Arregui

Abstract: Large-amplitude decaying kink oscillations of coronal loops are strongly influenced by nonlinear processes, such as Kelvin-Helmholtz instability (KHI) and turbulence, though comprehensive theory and observational confirmation remain limited. Building on the recently developed theory on nonlinear damping by KHI-induced turbulence in impulsively driven transverse loop oscillations, we investigate it… ▽ More Large-amplitude decaying kink oscillations of coronal loops are strongly influenced by nonlinear processes, such as Kelvin-Helmholtz instability (KHI) and turbulence, though comprehensive theory and observational confirmation remain limited. Building on the recently developed theory on nonlinear damping by KHI-induced turbulence in impulsively driven transverse loop oscillations, we investigate its observational signatures using 3D magnetohydrodynamic simulations and forward-modelled EUV images. The simulated oscillations exhibit time-varying frequency shifts and damping rates, which are broadly consistent with nonlinear turbulence-damping theory. Additionally, they exhibit excitation of higher-order modes, slightly increased periods relative to the linear kink period, and reduced displacement amplitudes. These features are generally preserved in synthetic observations, though resolving higher-order modes requires higher spatial resolution than currently available. For loops embedded in a hotter background, hotter channels (e.g., 193 Angstroms) are more sensitive to boundary dynamics, thus their oscillations decay faster with smaller displacements and larger phase shifts than those in cooler channels (e.g., 171 Angstroms). Comparisons of simulated and synthetic oscillations show close agreement at the early stage. At later times, synthetic oscillations exhibit smaller displacements and larger phase shifts, due to turbulence-induced asymmetry in the loop cross-section. Bayesian fitting shows that the initial oscillation amplitude and kink period are robustly constrained, whereas parameters controlling the damping profile are degenerate, indicating that additional observables would aid reliable seismological inference. These results provide a quantitative basis for identifying nonlinear damping and detecting KHI-driven turbulence in transverse loop oscillations. △ Less

Submitted 12 February, 2026; originally announced February 2026.

Comments: 22 pages, 9 figures, 3 tables, accepted by ApJ

Doppler-induced continuous spectral broadening of ultraviolet lasers

Authors: Huanhuan Wu, Yuhan Liu, Shengqiang Zhong, Yaozhi Yi, Zhuwen Lin, Hongwei Yin, Yilin Xu, Fan Yang, Xiantao Jiang, Yao Zhao

Abstract: We propose a compact scheme based on ultrafast-rotating phase plates (URPPs) to achieve continuous spectral broadening of ultraviolet lasers. The rapid rotation elements behave as a random oscillator which induces Doppler frequency shift into the ultraviolet lasers. As an example, for a disk-shaped phase plate, with the beam acting on the edge at a radius of 10 cm, a rotation frequency of 1 kHz, a… ▽ More We propose a compact scheme based on ultrafast-rotating phase plates (URPPs) to achieve continuous spectral broadening of ultraviolet lasers. The rapid rotation elements behave as a random oscillator which induces Doppler frequency shift into the ultraviolet lasers. As an example, for a disk-shaped phase plate, with the beam acting on the edge at a radius of 10 cm, a rotation frequency of 1 kHz, and a phase-element size of 10 nm, the continuous spectral broadening reaches 0.07%. Further increasing the rotation speed or reducing the phase-element can lead to greater spectral broadening. When multiple URPPs are arranged in series, the superimposed spatiotemporal modulation further enhances the continuous spectral broadening and achieves more effective speckle smoothing. The scheme is applicable to broadening the independent spectrum of optical frequency combs as well as to the mitigation of laser-plasma instabilities in inertial fusion energy. △ Less

Submitted 18 December, 2025; originally announced December 2025.

Comments: 13 pages, 5 figures

A 50-min coronal kink oscillation and its possible photospheric counterpart

Authors: Sihui Zhong, Valery M. Nakariakov, Dmitrii Y. Kolotkov

Abstract: A coronal loop of 290~Mm length, observed at 171~Å with SDO/AIA on February 6th 2024 near AR 13571, is found to oscillate with two significantly different oscillation periods, $48.8 \pm 6.1$~min and $4.8\pm 0.3$~min. The oscillations occur in the time intervals without detected flares or eruptions. Simultaneously, near the Northern footpoint of the oscillating loop, we detect a $49.6 \pm 5.0$-min… ▽ More A coronal loop of 290~Mm length, observed at 171~Å with SDO/AIA on February 6th 2024 near AR 13571, is found to oscillate with two significantly different oscillation periods, $48.8 \pm 6.1$~min and $4.8\pm 0.3$~min. The oscillations occur in the time intervals without detected flares or eruptions. Simultaneously, near the Northern footpoint of the oscillating loop, we detect a $49.6 \pm 5.0$-min periodic variation of the average projected photospheric magnetic field observed with SDO/HMI. The shorter-period decayless oscillation is attributed to the eigen-mode, standing kink oscillation of the loop, while the longer-period oscillation may be the oscillatory motion caused by the periodic footpoint driver. The photospheric long-period process can also drive the short-period, eigen oscillation of the loop via the self-oscillatory, \lq\lq violin\rq\rq\, mechanism, in which a transverse oscillation is excited by an external quasi-steady flow. This finding indicates that the most powerful, lower-frequency spectral components of photospheric motions, which are well below the Alfvénic/kink cutoff, can reach the corona. △ Less

Submitted 14 October, 2025; originally announced October 2025.

Comments: 9 pages, 6 figures, accepted for publication in ApJL

Packaging of Low-Environmental-Sensitivity WGM Resonators for Practical Applications

Authors: Jiajun Wu, Xuanqi Wang, Chengyu Zhang, Chenghong Li, Shan Zhong, Songbai Kang

Abstract: We present a prism-coupled packaging strategy for whispering-gallery mode resonators (WGMRs). Utilizing an all-solid-state optical adhesive process with active temperature control and hermetic sealing, the package exhibits exceptional long-term stability and environmental robustness. A standalone WGMR module was characterized, demonstrating a temperature sensitivity below 10^-7 /°C and a low-frequ… ▽ More We present a prism-coupled packaging strategy for whispering-gallery mode resonators (WGMRs). Utilizing an all-solid-state optical adhesive process with active temperature control and hermetic sealing, the package exhibits exceptional long-term stability and environmental robustness. A standalone WGMR module was characterized, demonstrating a temperature sensitivity below 10^-7 /°C and a low-frequency Z-axis acceleration sensitivity below 10^-10 /g. The module was applied as a stable optical frequency reference, achieving a short-term frequency stability of 2x10^-13 at 2 ms, and as a nonlinear photonic platform, generating Kerr soliton microcombs with a pump power of 100 mW. This compact, robust packaging solution enhances the applicability of WGMRs in real-world applications such as narrow-linewidth lasers and portable microcombs, facilitating the transition from laboratory research to practical deployment. △ Less

Submitted 12 October, 2025; originally announced October 2025.

Chip-Scale Rydberg Atomic Electrometer

Authors: Ren-Hao Xing, Ming-Yong Jing, Yue-Xiao Yan, Mu Xiang, Qing-Yi Meng, Shan Zhong, Hong-Hua Fang, Hong-Bo Sun

Abstract: An ideal electrometer should measure electric fields accurately while causing minimal disturbance to the field itself. Rydberg atomic electrometers are promising candidates for ideal electrometry due to their SI traceability and non-invasive nature. However, in practice, the atomic vapor cell shell can distort the electric field, limiting the device's performance. In this work, we overcome this ch… ▽ More An ideal electrometer should measure electric fields accurately while causing minimal disturbance to the field itself. Rydberg atomic electrometers are promising candidates for ideal electrometry due to their SI traceability and non-invasive nature. However, in practice, the atomic vapor cell shell can distort the electric field, limiting the device's performance. In this work, we overcome this challenge by fabricating a chip-scale vapor cell using a novel combination of femtosecond laser writing and optical contact. This method enables the development of a non-invasive atomic electrometer with a radar cross-section (RCS) 20 dB lower than that of commercial atomic cell-based electrometers. Furthermore, we observe a new sub-Doppler spectral narrowing phenomenon in these chip-scale cells. The effect originates from an incoherent, collision-driven mechanism--hereafter referred to as incoherent Dicke narrowing (ICDN). This advancement supports future revisions to the international system of units and broadens applications in metrology and quantum measurement. △ Less

Submitted 25 August, 2025; originally announced August 2025.

Identification of Nonlinear Damping of Transverse Loop Oscillations by KHI-induced Turbulence

Authors: Sihui Zhong, Andrew Hillier, Iñigo Arregui

Abstract: Kink oscillations in coronal loops have been extensively studied for their potential contributions to coronal heating and their role in plasma diagnostics through coronal seismology. A key focus is the strong damping of large-amplitude kink oscillations, which observational evidence suggests is nonlinear. However, directly identifying the nonlinearity is a challenge. This work presents an analytic… ▽ More Kink oscillations in coronal loops have been extensively studied for their potential contributions to coronal heating and their role in plasma diagnostics through coronal seismology. A key focus is the strong damping of large-amplitude kink oscillations, which observational evidence suggests is nonlinear. However, directly identifying the nonlinearity is a challenge. This work presents an analytic formula describing nonlinear standing kink oscillations dissipated by turbulence, characterised by a time-varying damping rate and period drift. We investigate how the damping behaviour depends on the driving amplitude and loop properties, showing that the initial damping time $τ$ is inversely proportional to the velocity disturbance over the loop radius, $V_i/R$. Using MCMC fitting with Bayesian inference, the nonlinear function better fits an observed decaying kink oscillation than traditional linear models, including exponential damping, suggesting its nonlinear nature. By applying a Bayesian model comparison, we establish regimes in which nonlinear and linear resonant absorption mechanisms dominate based on the relationship between the damping rate $τ/P$ and $V_i/R$. Additionally, analysis of two specific events reveals that while one favours the nonlinear model, the other is better explained by the linear model. Our results suggest that this analytical approximation of nonlinear damping due to turbulence provides a valid and reliable description of large-amplitude decaying kink oscillations in coronal loops. △ Less

Submitted 22 August, 2025; originally announced August 2025.

Comments: 21 pages, 9 figures, 3 tables, accepted by ApJ

Light Storage and Retrieval in an Atomic Tripod System

Authors: Shan Zhong, A. J. Sudler, D. Blume, Alberto M. Marino

Abstract: Highly-efficient quantum memories are essential for advancing quantum information processing technologies, including scalable quantum computing and quantum networks. We experimentally demonstrate a light storage and retrieval protocol in a tripod system using an ensemble of laser-cooled $^{87}$Rb atoms. The tripod system, which consists of three ground states and an excited state, offers rich dyna… ▽ More Highly-efficient quantum memories are essential for advancing quantum information processing technologies, including scalable quantum computing and quantum networks. We experimentally demonstrate a light storage and retrieval protocol in a tripod system using an ensemble of laser-cooled $^{87}$Rb atoms. The tripod system, which consists of three ground states and an excited state, offers rich dynamics: its use to coherently store and retrieve a weak probe pulse in the $^{87}$Rb $F=1$ ground state manifold leads to the interference of two spin-wave excitations during storage time that translate to an interference in the peak intensity of the retrieved probe pulse. Our work shows that these interferences, which manifest when varying the pulse sequence or energy level structure, can be controlled experimentally by varying the storage time, optical phase, and magnetic field strength. Theoretical simulations exhibit excellent agreement with the experimental results. This work demonstrates the rich dynamics and versatile capabilities of atomic tripod systems for light storage and retrieval, with key advantages over conventional $Λ$-systems, highlighting the potential of atomic tripod systems for applications in quantum information processing, quantum synchronization, and atomic memory protocols. △ Less

Submitted 13 August, 2025; originally announced August 2025.

A Driving Regime-Embedded Deep Learning Framework for Modeling Intra-Driver Heterogeneity in Multi-Scale Car-Following Dynamics

Authors: Shirui Zhou, Jiying Yan, Junfang Tian, Tao Wang, Yongfu Li, Shiquan Zhong

Abstract: A fundamental challenge in car-following modeling lies in accurately representing the multi-scale complexity of driving behaviors, particularly the intra-driver heterogeneity where a single driver's actions fluctuate dynamically under varying conditions. While existing models, both conventional and data-driven, address behavioral heterogeneity to some extent, they often emphasize inter-driver hete… ▽ More A fundamental challenge in car-following modeling lies in accurately representing the multi-scale complexity of driving behaviors, particularly the intra-driver heterogeneity where a single driver's actions fluctuate dynamically under varying conditions. While existing models, both conventional and data-driven, address behavioral heterogeneity to some extent, they often emphasize inter-driver heterogeneity or rely on simplified assumptions, limiting their ability to capture the dynamic heterogeneity of a single driver under different driving conditions. To address this gap, we propose a novel data-driven car-following framework that systematically embeds discrete driving regimes (e.g., steady-state following, acceleration, cruising) into vehicular motion predictions. Leveraging high-resolution traffic trajectory datasets, the proposed hybrid deep learning architecture combines Gated Recurrent Units for discrete driving regime classification with Long Short-Term Memory networks for continuous kinematic prediction, unifying discrete decision-making processes and continuous vehicular dynamics to comprehensively represent inter- and intra-driver heterogeneity. Driving regimes are identified using a bottom-up segmentation algorithm and Dynamic Time Warping, ensuring robust characterization of behavioral states across diverse traffic scenarios. Comparative analyses demonstrate that the framework significantly reduces prediction errors for acceleration (maximum MSE improvement reached 58.47\%), speed, and spacing metrics while reproducing critical traffic phenomena, such as stop-and-go wave propagation and oscillatory dynamics. △ Less

Submitted 6 June, 2025; originally announced June 2025.

Unveiling hole-facilitated amorphisation in pressure-induced phase transformation of silicon

Authors: Tong Zhao, Shulin Zhong, Yuxin Sun, Defan Wu, Chunyi Zhang, Rui Shi, Hao Chen, Zhenyi Ni, Xiaodong Pi, Xiangyang Ma, Yunhao Lu, Deren Yang

Abstract: Pressure-induced phase transformation occurs during silicon (Si) wafering processes. \b{eta}-tin (Si-II) phase is formed at high pressures, followed by the transformation to Si-XII, Si-III or/and amorphous Si (α-Si) phases during the subsequent decompression. While the imposed pressure and its release rate are known to dictate the phase transformation of Si, the effect of charge carriers are ignor… ▽ More Pressure-induced phase transformation occurs during silicon (Si) wafering processes. \b{eta}-tin (Si-II) phase is formed at high pressures, followed by the transformation to Si-XII, Si-III or/and amorphous Si (α-Si) phases during the subsequent decompression. While the imposed pressure and its release rate are known to dictate the phase transformation of Si, the effect of charge carriers are ignored. Here, we experimentally unveil that the increased hole concentration facilitates the amorphization in the pressure-induced phase transformation of Si. The underlying mechanism is elucidated by the theoretical calculations based on machine-learning interatomic potentials. The hole-facilitated amorphization is also experimentally confirmed to occur in the indented Ge, GaAs or SiC. We discover that hole concentration is another determining factor for the pressure-induced phase transformations of the industrially important semiconductors. △ Less

Submitted 5 December, 2024; originally announced December 2024.

Intermittency of bubble deformation in turbulence

Authors: Xu Xu, Yinghe Qi, Shijie Zhong, Shiyong Tan, Qianwen Wu, Rui Ni

Abstract: The deformation of finite-sized bubbles in intense turbulence exhibits complex geometries beyond simple spheroids as the bubbles exchange energy with the surrounding eddies across a wide range of scales. This study investigates deformation via the velocity of the most stretched tip of the deformed bubble in 3D, as the tip extension results from the compression of the rest of the interface by surro… ▽ More The deformation of finite-sized bubbles in intense turbulence exhibits complex geometries beyond simple spheroids as the bubbles exchange energy with the surrounding eddies across a wide range of scales. This study investigates deformation via the velocity of the most stretched tip of the deformed bubble in 3D, as the tip extension results from the compression of the rest of the interface by surrounding eddies. The results show that the power spectrum based on the tip velocity exhibits a scaling akin to that of the Lagrangian statistics of fluid elements, but decays with a distinct timescale and magnitude modulated by the Weber number based on the bubble size. This indicates that the interfacial energy is primarily siphoned from eddies of similar sizes as the bubble. Moreover, the tip velocity appears much more intermittent than the velocity increment, and its distribution near the extreme tails can be explained by the proposed model that accounts for the fact that small eddies with sufficient energy can contribute to extreme deformation. These findings provide a framework for understanding the energy transfer between deformable objects and multiscale eddies in intense turbulence. △ Less

Submitted 28 October, 2024; originally announced October 2024.

Journal ref: Phys. Rev. Lett. 133, 214001 (2024)

Functional Ultrasound Imaging Combined with Machine Learning for Whole-Brain Analysis of Drug-Induced Hemodynamic Changes

Authors: Jared Deighton, Shan Zhong, Kofi Agyeman, Wooseong Choi, Charles Liu, Darrin Lee, Vasileios Maroulas, Vasileios Christopoulos

Abstract: Functional ultrasound imaging (fUSI) is a cutting-edge technology that measures changes in cerebral blood volume (CBV) by detecting backscattered echoes from red blood cells moving within its field of view (FOV). It offers high spatiotemporal resolution and sensitivity, allowing for detailed visualization of cerebral blood flow dynamics. While fUSI has been utilized in preclinical drug development… ▽ More Functional ultrasound imaging (fUSI) is a cutting-edge technology that measures changes in cerebral blood volume (CBV) by detecting backscattered echoes from red blood cells moving within its field of view (FOV). It offers high spatiotemporal resolution and sensitivity, allowing for detailed visualization of cerebral blood flow dynamics. While fUSI has been utilized in preclinical drug development studies to explore the mechanisms of action of various drugs targeting the central nervous system, many of these studies rely on predetermined regions of interest (ROIs). This focus may overlook relevant brain activity outside these specific areas, which could influence the results. To address this limitation, we compared three machine learning approaches-convolutional neural network (CNN), support vector machine (SVM), and vision transformer (ViT)-combined with fUSI to analyze the pharmacodynamics of Dizocilpine (MK-801), a potent non-competitive NMDA receptor antagonist commonly used in preclinical models for memory and learning impairments. While all three machine learning techniques could distinguish between drug and control conditions, CNN proved particularly effective due to their ability to capture hierarchical spatial features while maintaining anatomical specificity. Class activation mapping revealed brain regions, including the prefrontal cortex and hippocampus, that are significantly affected by drug administration, consistent with the literature reporting a high density of NMDA receptors in these areas. Overall, the combination of fUSI and CNN creates a novel analytical framework for examining pharmacological mechanisms, allowing for data-driven identification and regional mapping of drug effects while preserving anatomical context and physiological relevance. △ Less

Submitted 19 August, 2025; v1 submitted 12 October, 2024; originally announced October 2024.

Comments: 24 pages, 6 figures

The oscillating and vibrating cylinder: a benchmark to study low Mach number aeroacoustics

Authors: Étienne Spieser, Siyang Zhong, Xin Zhang

Abstract: Hydrodynamic and acoustic scales separate as the Mach number decreases, making the modelling of aeroacoustic phenomena singular in this flow regime. The benchmark of the flow developing around an oscillating and vibrating cylinder is one of the scarce configuration that is fully analytically tractable, and is thus precious in the validation of new theories or solvers. This work carefully derives t… ▽ More Hydrodynamic and acoustic scales separate as the Mach number decreases, making the modelling of aeroacoustic phenomena singular in this flow regime. The benchmark of the flow developing around an oscillating and vibrating cylinder is one of the scarce configuration that is fully analytically tractable, and is thus precious in the validation of new theories or solvers. This work carefully derives the complete incompressible flow solution for this case, extending the axisymmetric results of the literature to more complex cylinder motion. High-order finite element method solution of the incompressible Navier-Stokes equations provide a reference to validate the analytical formulae derived here. Both analytical and numerical investigations agree on an independence of the configuration to the Reynolds number. Up to the critical Reynolds number, found to lie above $10^4$, the hydrodynamic solution of this configuration is solely governed by the Stokes number. The exact expression of the sound radiated in the far field is computed by accounting for the cylinder scattering by means of tailored Green's functions. △ Less

Submitted 8 August, 2024; originally announced August 2024.

WGMR Self-Injection Locking Method Based on Enhanced Optical Feedback with Auxiliary Prism

Authors: Jiajun Wu, Shan Zhong, Songbai Kang

Abstract: The optical feedback intensity is an important parameter for realizing narrow linewidth lasers in Whispering-gallery-mode resonator (WGMR) self-injection locking technology. We proposed an approach that enhances the intensity of intracavity feedback in crystalline WGMR by using only a single coated auxiliary prism. Compared to the Rayleigh scattering, the feedback intensity of the enhanced scheme… ▽ More The optical feedback intensity is an important parameter for realizing narrow linewidth lasers in Whispering-gallery-mode resonator (WGMR) self-injection locking technology. We proposed an approach that enhances the intensity of intracavity feedback in crystalline WGMR by using only a single coated auxiliary prism. Compared to the Rayleigh scattering, the feedback intensity of the enhanced scheme increased by more than a hundred times. Furthermore, we demonstrated that, with the enhanced approach, the instantaneous linewidth of the laser was suppressed to 7 Hz level, the locking range was expanded up to 8 GHz, and the relative intensity noise (RIN) was reduced to -152 dBc/Hz@10MHz. The feedback enhanced design is compact, easy-to-operated and can be integrated with the WGMR. It provides a miniaturized solution for controlling optical feedback intensity in WGMR self-injection locking technology. △ Less

Submitted 18 March, 2024; originally announced April 2024.

Diagnostics of the solar coronal plasmas by magnetohydrodynamic waves: Magnetohydrodynamic seismology

Authors: Valery M. Nakariakov, Sihui Zhong, Dmitrii Y. Kolotkov, Rebecca L. Meadowcroft, Yu Zhong, Ding Yuan

Abstract: Macroscopic wave and oscillatory phenomena ubiquitously detected in the plasma of the corona of the Sun are interpreted in terms of magnetohydrodynamic theory. Fast and slow magnetoacoustic waves are clearly distinguished in observations. Properties of coronal magnetohydrodynamic waves are determined by local parameters of the plasma, including the field-aligned filamentation typical for the coron… ▽ More Macroscopic wave and oscillatory phenomena ubiquitously detected in the plasma of the corona of the Sun are interpreted in terms of magnetohydrodynamic theory. Fast and slow magnetoacoustic waves are clearly distinguished in observations. Properties of coronal magnetohydrodynamic waves are determined by local parameters of the plasma, including the field-aligned filamentation typical for the corona. It makes coronal magnetohydrodynamic waves reliable probes of the coronal plasma structures by the method of magnetohydrodynamic seismology. For example, propagating slow waves indicate the local direction of the guiding magnetic field. Standing, sloshing and propagating slow waves can be used for probing the coronal heating function and the polytropic index. Kink oscillations of coronal plasma loops provide us with the estimations of the absolute value of the magnetic field in oscillating plasma loops. This tutorial introduces several techniques of magnetohydrodynamic seismology of solar coronal plasmas. It includes the description of practical steps in the data acquisition, pre-processing, and processing using the open-access data of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory spacecraft, and elaborated data analysis techniques of motion magnification and Bayesian statistics. △ Less

Submitted 29 March, 2024; originally announced April 2024.

Comments: 39 pages, 12 figures, accepted for publication in Reviews of Modern Plasma Physics

Breaking bubbles across multiple timescales in turbulence

Authors: Yinghe Qi, Xu Xu, Shiyong Tan, Shijie Zhong, Qianwen Wu, Rui Ni

Abstract: The familiar process of bubbles generated via breaking waves in the ocean is foundational to many natural and industrial applications. In this process, large pockets of entrained gas are successively fragmented by the ambient turbulence into smaller and smaller bubbles. The key question is how long it takes for the bubbles to reach terminal sizes for a given system. Despite decades of effort, the… ▽ More The familiar process of bubbles generated via breaking waves in the ocean is foundational to many natural and industrial applications. In this process, large pockets of entrained gas are successively fragmented by the ambient turbulence into smaller and smaller bubbles. The key question is how long it takes for the bubbles to reach terminal sizes for a given system. Despite decades of effort, the reported breakup time from multiple experiments differs significantly. Here, to reconcile those results, rather than focusing on one scale, we measure multiple timescales associated with the process through a unique experiment that resolves bubbles' local deformation and curvature. The results emphasize that the scale separation among various timescales is controlled by the Weber number, similar to how the Reynolds number determines the scale separation in single-phase turbulence, but shows a distinct transition at a critical Weber number. △ Less

Submitted 18 January, 2024; originally announced January 2024.

Journal ref: Journal of Fluid Mechanics. 2024;983:A24

Numerical study on the effects of fluid properties in electrohydrodynamic pulsating jet under constant voltage

Authors: Yaohui Lu, Songyi Zhong, Kai Leong Chong, Yang Yang, Tao Yue, Quan Zhang, Long Li

Abstract: Pulsating jet is one of the common working modes in electrohydrodynamic printing (EHDP) that process is highly affected by operating parameters and material properties. In this paper, the processes of pulsating jet for liquids with different physical properties were investigated using numerical simulation. An electrohydrodynamic solver was established, and a charge flux restricting step was adopte… ▽ More Pulsating jet is one of the common working modes in electrohydrodynamic printing (EHDP) that process is highly affected by operating parameters and material properties. In this paper, the processes of pulsating jet for liquids with different physical properties were investigated using numerical simulation. An electrohydrodynamic solver was established, and a charge flux restricting step was adopted to ensure a realistic distribution of free charges. Three various ejection regimes were observed in our simulations: oscillating cone (OC), choked jet (CJ), and stable cone-jet (SJ). We found that three dimensionless numbers relating to liquid properties determined the ejection regime: the Ohnesorge number, Q0εr/Q, and Q0/(QRe). Based on those dimensionless numbers, the roles of liquid properties on pulsating jet (OC and CJ) were analyzed. In OC, the break of the jet is due to the significant oscillation of the Taylor cone, which is mainly affected by viscosity and conductivity. In CJ, the jet emission is terminated by the excessive resistant force in the cone-jet transition region. For liquids with low and medium viscosity, the dominant resistant force is the polarization force or viscous force when εrRe is larger or smaller than 1, respectively. For high viscosity liquids, the viscous force always becomes the major resistance. These results further reveal the physical mechanism of pulsating jet and can be used to guide its application. △ Less

Submitted 12 September, 2023; originally announced September 2023.

On the breakup frequency of bubbles and droplets in turbulence: a compilation and evaluation of experimental data

Authors: Shijie Zhong, Rui Ni

Abstract: The dispersed phase in liquid-liquid emulsions and air-liquid mixtures can often be fragmented into smaller sizes by the surrounding turbulent carrier phase. The critical parameter that controls this process is the breakup frequency, which is defined from the breakup kernel in the population balance equation. The breakup frequency controls how long it takes for the dispersed phase reaches the term… ▽ More The dispersed phase in liquid-liquid emulsions and air-liquid mixtures can often be fragmented into smaller sizes by the surrounding turbulent carrier phase. The critical parameter that controls this process is the breakup frequency, which is defined from the breakup kernel in the population balance equation. The breakup frequency controls how long it takes for the dispersed phase reaches the terminal size distribution for given turbulence. In this article, we try to summarize the key experimental results and compile the existing datasets under a consistent framework to find out what is the characteristic timescale of the problem and how to account for the inner density and viscosity of the dispersed phase. Furthermore, by pointing out the inconsistency of existing experimental data, the key important unsolved questions and related problems on the breakup frequency of bubbles and droplets are discussed. △ Less

Submitted 26 August, 2023; originally announced August 2023.

Polarisation of decayless kink oscillations of solar coronal loops

Authors: Sihui Zhong, Valery M. Nakariakov, Dmitrii Y. Kolotkov, Lakshmi Pradeep Chitta, Patrick Antolin, Cis Verbeeck, David Berghmans

Abstract: Decayless kink oscillations of plasma loops in the solar corona may contain an answer to the enigmatic problem of solar and stellar coronal heating. The polarisation of the oscillations gives us a unique information about their excitation mechanisms and energy supply. However, unambiguous determination of the polarisation has remained elusive. Here, we show simultaneous detection of a 4-min decayl… ▽ More Decayless kink oscillations of plasma loops in the solar corona may contain an answer to the enigmatic problem of solar and stellar coronal heating. The polarisation of the oscillations gives us a unique information about their excitation mechanisms and energy supply. However, unambiguous determination of the polarisation has remained elusive. Here, we show simultaneous detection of a 4-min decayless kink oscillation from two non-parallel lines-of-sights, separated by about 104\textdegree, provided by unique combination of the High Resolution Imager on Solar Orbiter and the Atmospheric Imaging Assembly on Solar Dynamics Observatory. The observations reveal a horizontal or weakly oblique linear polarisation of the oscillation. This conclusion is based on the comparison of observational results with forward modelling of the observational manifestation of various kinds of polarisation of kink oscillations. The revealed polarisation favours the sustainability of these oscillations by quasi-steady flows which may hence supply the energy for coronal heating. △ Less

Submitted 21 August, 2023; originally announced August 2023.

Comments: 19 pages, 7 figures, accepted to Nature Communications

30-min Decayless Kink Oscillations in a Very Long Bundle of Solar Coronal Plasma Loops

Authors: Sihui Zhong, Valery M. Nakariakov, Yuhu Miao, Libo Fu, Ding Yuan

Abstract: The energy balance in the corona of the Sun is the key to the long-standing coronal heating dilemma, which could be potentially revealed by observational studies of decayless kink oscillations of coronal plasma loops. A bundle of very long off-limb coronal loops with the length of $736\pm80$ Mm and a lifetime of about 2 days are found to exhibit decayless kink oscillations. The oscillations were o… ▽ More The energy balance in the corona of the Sun is the key to the long-standing coronal heating dilemma, which could be potentially revealed by observational studies of decayless kink oscillations of coronal plasma loops. A bundle of very long off-limb coronal loops with the length of $736\pm80$ Mm and a lifetime of about 2 days are found to exhibit decayless kink oscillations. The oscillations were observed for several hours. The oscillation amplitude was measured at 0.3-0.5 Mm, and the period at 28-33 min. The existence of 30-min periodicity of decayless kink oscillations indicates that the mechanism compensating the wave damping is still valid in such a massive plasma structure. It provides important evidence for the non-resonant origin of decayless kink oscillations with 2-6min periods, i.e., the lack of their link with the leakage of photospheric and chromospheric oscillations into the corona and the likely role of the broadband energy sources. Magnetohydrodynamic seismology based on the reported detection of the kink oscillation, with the assistance of the differential emission measure analysis and a background coronal model provides us with a comprehensive set of plasma and magnetic field diagnostics, which is of interest as input parameters of space weather models. △ Less

Submitted 10 August, 2023; originally announced August 2023.

Comments: 15 pages, 5 figures, accepted by Scientific Reports

Ultra-stable and versatile high-energy resolution setup for attosecond photoelectron spectroscopy

Authors: Sizuo Luo, Robin Weissenbilder, Hugo Laurell, Mattias Ammitzböll, Vénus Poulain, David Busto, Lana Neoričić, Chen Guo, Shiyang Zhong, David Kroon, Richard J Squibb, Raimund Feifel, Mathieu Gisselbrecht, Anne L'Huillier, Cord L Arnold

Abstract: Attosecond photoelectron spectroscopy is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline. The active-stabilization system can remain ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning… ▽ More Attosecond photoelectron spectroscopy is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline. The active-stabilization system can remain ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning range of \sim 400 fs. A tunable femtosecond laser source to drive high-order harmonic generation allows for precisely addressing atomic and molecular resonances. Furthermore, the interferometer includes a spectral shaper in 4f-geometry in the probe arm as well as a tunable bandpass filter in the pump arm, which offer additional high flexibility in terms of tunability as well as narrowband or polychromatic probe pulses. We show that spectral phase measurements of photoelectron wavepackets with the rainbow RABBIT technique (reconstruction of attosecond beating by two photon transitions) with narrowband probe pulses can significantly improve the photoelectron energy resolution. In this setup, the temporal-spectral resolution of photoelectron spectroscopy can reach a new level of accuracy and precision. △ Less

Submitted 21 January, 2023; originally announced January 2023.

Coherent control of wave beams via unidirectional evanescent modes excitation

Authors: Shuomin Zhong, Xuchen Wang, Sergei A. Tretyakov

Abstract: Conventional coherent absorption occurs only when two incident beams exhibit mirror symmetry with respect to the absorbing surface, i.e., the two beams have the same incident angles, phases, and amplitudes. In this work, we propose a more general metasurface paradigm for coherent perfect absorption, with impinging waves from arbitrary asymmetric directions. By exploiting excitation of unidirection… ▽ More Conventional coherent absorption occurs only when two incident beams exhibit mirror symmetry with respect to the absorbing surface, i.e., the two beams have the same incident angles, phases, and amplitudes. In this work, we propose a more general metasurface paradigm for coherent perfect absorption, with impinging waves from arbitrary asymmetric directions. By exploiting excitation of unidirectional evanescent waves, the output can be fixed at one reflection direction for any amplitude and phase of the control wave. We show theoretically and confirm experimentally that the relative amplitude of the reflected wave can be tuned continuously from zero to unity by changing the phase difference between the two beams, i.e. switching from coherent perfect absorption to full reflection. We hope that this work will open up promising possibilities for wave manipulation via evanescent waves engineering with applications in optical switches, one-side sensing, and radar cross section control. △ Less

Submitted 8 January, 2023; originally announced January 2023.

Comments: 12 pages, 6 figures

Resonant two-photon ionization of helium atoms studied by attosecond interferometry

Authors: Lana Neoričić, David Busto, Hugo Laurell, Robin Weissenbilder, Mattias Ammitzböll, Sizuo Luo, Jasper Peschel, Hampus Wikmark, Jan Lahl, Sylvain Maclot, Richard James Squibb, Shiyang Zhong, Per Eng-Johnsson, Cord Louis Arnold, Raimund Feifel, Mathieu Gisselbrecht, Eva Lindroth, Anne L'Huillier

Abstract: We study resonant two-photon ionization of helium atoms via the $1s3p$, $1s4p$ and $1s5p^1$P$_1$ states using the 15$^\mathrm{th}$ harmonic of a titanium-sapphire laser for the excitation and a weak fraction of the laser field for the ionization. The phase of the photoelectron wavepackets is measured by an attosecond interferometric technique, using the 17$^\mathrm{th}$ harmonic. We perform experi… ▽ More We study resonant two-photon ionization of helium atoms via the $1s3p$, $1s4p$ and $1s5p^1$P$_1$ states using the 15$^\mathrm{th}$ harmonic of a titanium-sapphire laser for the excitation and a weak fraction of the laser field for the ionization. The phase of the photoelectron wavepackets is measured by an attosecond interferometric technique, using the 17$^\mathrm{th}$ harmonic. We perform experiments with angular resolution using a velocity map imaging spectrometer and with high energy resolution using a magnetic bottle electron spectrometer. Our results are compared to calculations using the two-photon random phase approximation with exchange to account for electron correlation effects. We give an interpretation for the multiple $π$-rad phase jumps observed, both at and away from resonance, as well as their dependence on the emission angle. △ Less

Submitted 28 June, 2022; originally announced June 2022.

High-Performance Mid-IR to Deep-UV van der Waals Photodetectors Capable of Local Spectroscopy at Room Temperature

Authors: Daozhi Shen, HeeBong Yang, Christian Spudat, Tarun Patel, Shazhou Zhong, Fangchu Chen, Jian Yan, Xuan Luo, Meixin Cheng, German Sciaini, Yuping Sun, Daniel A. Rhodes, Thomas Timusk, Y. Norman Zhou, Na Young Kim, Adam W. Tsen

Abstract: The ability to perform broadband optical spectroscopy with sub-diffraction-limit resolution is highly sought-after for a wide range of critical applications. However, sophisticated tip-enhanced techniques are currently required to achieve this goal. We bypass this challenge by demonstrating an extremely broadband photodetector based on a two-dimensional (2D) van der Waals heterostructure that is s… ▽ More The ability to perform broadband optical spectroscopy with sub-diffraction-limit resolution is highly sought-after for a wide range of critical applications. However, sophisticated tip-enhanced techniques are currently required to achieve this goal. We bypass this challenge by demonstrating an extremely broadband photodetector based on a two-dimensional (2D) van der Waals heterostructure that is sensitive to light across over a decade in energy from the mid-infrared (MIR) to deep-ultraviolet (DUV) at room temperature. The devices feature high detectivity (> 10^9 cm Hz^1/2 W^-1) together with high bandwidth (2.1 MHz). The active area can be further miniaturized to submicron dimensions, far below the diffraction limit for the longest detectable wavelength of 4.1 um, enabling such devices for facile measurements of local optical properties on atomic-layer-thickness samples placed in close proximity. This work can lead to the development of low-cost and high-throughput photosensors for hyperspectral imaging at the nanoscale. △ Less

Submitted 25 February, 2022; v1 submitted 31 January, 2022; originally announced February 2022.

Comments: 12 pages: 7 pages main text, 5 pages figures

Studying ultrafast Rabi dynamics with a short-wavelength seeded free-electron laser

Authors: Saikat Nandi, Edvin Olofsson, Mattias Bertolino, Stefanos Carlström, Felipe Zapata, David Busto, Carlo Callegari, Michele Di Fraia, Per Eng-Johnsson, Raimund Feifel, Guillaume Gallician, Mathieu Gisselbrecht, Sylvain Maclot, Lana Neoričić, Jasper Peschel, Oksana Plekan, Kevin C. Prince, Richard J. Squibb, Shiyang Zhong, Philipp V. Demekhin, Michael Meyer, Catalin Miron, Laura Badano, Miltcho B. Danailov, Luca Giannessi , et al. (4 additional authors not shown)

Abstract: Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field. They are ubiquitous in physics with applications in different areas such as photonics, nano-electronics, electron microscopy, and quantum information. While the theory developed by Rabi was intended for fermions in gyrating magnetic fields, Autler and Townes realized that it could… ▽ More Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field. They are ubiquitous in physics with applications in different areas such as photonics, nano-electronics, electron microscopy, and quantum information. While the theory developed by Rabi was intended for fermions in gyrating magnetic fields, Autler and Townes realized that it could also be used to describe coherent light-matter interaction within the rotating wave approximation\cite. Although intense nanometer-wavelength light-sources have been available for more than a decade, Rabi dynamics at such short wavelengths have not been observed directly. Here we show that femtosecond extreme-ultraviolet pulses from a seeded free-electron laser can drive Rabi oscillations between the ground state and an excited state in helium atoms. The measured photoemission signal revealed an Autler-Townes doublet as well as an avoided crossing, phenomena that are both trademarks of quantum optics. Using theoretical analyses that go beyond the strong-field approximation, we found that the ultrafast build-up of the doublet structure follows from a quantum interference effect between resonant and non-resonant photoionization pathways. Given the recent availability of intense attosecond and few-femtosecond extreme-ultraviolet pulses, our results offer opportunities to carry out ultrafast manipulation of coherent processes at short wavelengths using free-electron lasers. △ Less

Submitted 26 January, 2022; originally announced January 2022.

Comments: 38 pages, 10 figures

Journal ref: Nature 608, 488-493 (2022)

Probing electronic decoherence with high-resolution attosecond photoelectron interferometry

Authors: David Busto, Hugo Laurell, Daniel Finkelstein Shapiro, Christina Alexandridi, Marcus Isinger, Saikat Nandi, Richard Squibb, Margherita Turconi, Shiyang Zhong, Cord Arnold, Raimund Feifel, Mathieu Gisselbrecht, Pascal Salières, Tönu Pullerits, Fernando Martín, Luca Argenti, Anne L'Huillier

Abstract: Quantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well known source of decoherence when only one of the particles is measured. Here we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon… ▽ More Quantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well known source of decoherence when only one of the particles is measured. Here we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon ionization via the 2s2p autoionizing state in He using high spectral resolution photoelectron interferometry. Combining experiment and theory, we show that the strong dipole coupling of the 2s2p and 2p$^2$ states results in the entanglement of the angular and radial degrees of freedom. This translates, in angle integrated measurements, into a dynamic loss of coherence during autoionization. △ Less

Submitted 23 November, 2021; originally announced November 2021.

Attosecond photoionization dynamics in the vicinity of the Cooper minima in argon

Authors: C. Alexandridi, D. Platzer, L. Barreau, D. Busto, S. Zhong, M. Turconi, L. Neoričić, H. Laurell, C. L. Arnold, A. Borot, J. -F. Hergott, O. Tcherbakoff, M. Lejman, M. Gisselbrecht, E. Lindroth, A. L'Huillier, J. M. Dahlström, P. Salières

Abstract: Using a spectrally resolved electron interferometry technique, we measure photoionization time delays between the $3s$ and $3p$ subshells of argon over a large 34-eV energy range covering the Cooper minima in both subshells. The observed strong variations of the $3s-3p$ delay difference, including a sign change, are well reproduced by theoretical calculations using the Two-Photon Two-Color Random… ▽ More Using a spectrally resolved electron interferometry technique, we measure photoionization time delays between the $3s$ and $3p$ subshells of argon over a large 34-eV energy range covering the Cooper minima in both subshells. The observed strong variations of the $3s-3p$ delay difference, including a sign change, are well reproduced by theoretical calculations using the Two-Photon Two-Color Random Phase Approximation with Exchange. Strong shake-up channels lead to photoelectrons spectrally overlapping with those emitted from the $3s$ subshell. These channels need to be included in our analysis to reproduce the experimental data. Our measurements provide a stringent test for multielectronic theoretical models aiming at an accurate description of inter-channel correlation. △ Less

Submitted 30 July, 2020; originally announced July 2020.

Journal ref: Phys. Rev. Research 3, 012012 (2021)

Attosecond electron-spin dynamics in Xe 4d photoionization

Authors: Shiyang Zhong, Jimmy Vinbladh, David Busto, Richard J. Squibb, Marcus Isinger, Lana Neoričić, Hugo Laurell, Robin Weissenbilder, Cord L. Arnold, Raimund Feifel, Jan Marcus Dahlström, Göran Wendin, Mathieu Gisselbrecht, Eva Lindroth, Anne L'Huillier

Abstract: The photoionization of xenon atoms in the 70-100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe$^+$ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past… ▽ More The photoionization of xenon atoms in the 70-100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe$^+$ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide new insight into the complex electron-spin dynamics of photo-induced phenomena. △ Less

Submitted 25 May, 2020; originally announced May 2020.

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

Authors: Bing Wang, Shuncong Zhong, Tung-Lik Lee, Kevin S Fancey, Jiawei Mi

Abstract: Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to load-carrying structures in aerospace, wind turbines, transportation, and medical equipment, etc. Thus robust and reliable non-destructive testing (NDT) of composites is essential to reduce safety concerns… ▽ More Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to load-carrying structures in aerospace, wind turbines, transportation, and medical equipment, etc. Thus robust and reliable non-destructive testing (NDT) of composites is essential to reduce safety concerns and maintenance costs. There have been various NDT methods built upon different principles for quality assurance during the whole lifecycle of a composite product. This paper reviews the most established NDT techniques for detection and evaluation of defects/damage evolution in composites. These include acoustic emission, ultrasonic testing, infrared thermography, terahertz testing, shearography, digital image correlation, as well as X-ray and neutron imaging. For each NDT technique, we cover a brief historical background, principles, standard practices, equipment and facilities used for composite research. We also compare and discuss their benefits and limitations, and further summarise their capabilities and applications to composite structures. Each NDT technique has its own potential and rarely achieves a full-scale diagnosis of structural integrity. Future development of NDT techniques for composites will be directed towards intelligent and automated inspection systems with high accuracy and efficient data processing capabilities. △ Less

Submitted 4 March, 2020; v1 submitted 27 February, 2020; originally announced February 2020.

Comments: 51 pages, 13 figures, 10 tables, 311 references

Journal ref: Advances in Mechanical Engineering 2020

Attosecond timing of electron emission from a molecular shape resonance

Authors: S. Nandi, E. Plésiat, S. Zhong, A. Palacios, D. Busto, M. Isinger, L. Neoričić, C. L. Arnold, R. J. Squibb, R. Feifel, P. Decleva, A. L'Huillier, F. Martín, M. Gisselbrecht

Abstract: Shape resonances in physics and chemistry arise from the spatial confinement of a particle by a potential barrier. In molecular photoionization, these barriers prevent the electron from escaping instantaneously, so that nuclei may move and modify the potential, thereby affecting the ionization process. By using an attosecond two-color interferometric approach in combination with high spectral reso… ▽ More Shape resonances in physics and chemistry arise from the spatial confinement of a particle by a potential barrier. In molecular photoionization, these barriers prevent the electron from escaping instantaneously, so that nuclei may move and modify the potential, thereby affecting the ionization process. By using an attosecond two-color interferometric approach in combination with high spectral resolution, we have captured the changes induced by the nuclear motion on the centrifugal barrier that sustains the well-known shape resonance in valence-ionized N$_2$. We show that despite the nuclear motion altering the bond length by only $2\%$, which leads to tiny changes in the potential barrier, the corresponding change in the ionization time can be as large as $200$ attoseconds. This result poses limits to the concept of instantaneous electronic transitions in molecules, which is at the basis of the Franck-Condon principle of molecular spectroscopy. △ Less

Submitted 13 August, 2020; v1 submitted 19 November, 2019; originally announced November 2019.

Comments: 24 pages, 5 figures

Journal ref: Sci. Adv. 6, eaba7762 (2020)

Generation and detection of coherent longitudinal acoustic waves in ultrathin 1T'-MoTe2

Authors: Nicolas Rivas, Shazhou Zhong, Tina Dekker, Meixin Cheng, Patrick Gicala, Fangchu Chen, Xuan Luo, Yuping Sun, Ariel A. Petruk, Kostyantyn Pichugin, Adam W. Tsen, German Sciaini

Abstract: Layered transition metal dichalcogenides have attracted substantial attention owing to their versatile functionalities and compatibility with current nanofabrication technologies. Thus, noninvasive means to determine the mechanical properties of nanometer (nm) thick specimens are of increasing importance. Here, we report on the detection of coherent longitudinal acoustic phonon modes generated by… ▽ More Layered transition metal dichalcogenides have attracted substantial attention owing to their versatile functionalities and compatibility with current nanofabrication technologies. Thus, noninvasive means to determine the mechanical properties of nanometer (nm) thick specimens are of increasing importance. Here, we report on the detection of coherent longitudinal acoustic phonon modes generated by impulsive femtosecond (fs) optical excitation. Broadband fs-transient absorption experiments in 1T'-MoTe2 flakes as a function of thickness (7 nm - 30 nm) yield a longitudinal sound speed of 2990 m/s. In addition, temperature dependent measurements unveil a linear decrease of the normalized Young's modulus with a slope of -0.002 per K and no noticeable change caused by the Td - 1T' structural phase transition or variations in film thickness. △ Less

Submitted 13 November, 2019; originally announced November 2019.

Comments: The following article has been accepted by Applied Physics Letters

FPGA-Controlled Versatile Microwave Source for Cold Atom Experiments

Authors: Isaiah Morgenstern, Shan Zhong, Qimin Zhang, Logan Baker, Jeremy Norris, Bao Tran, Arne Schwettmann

Abstract: We present a microwave source that is controlled by a commercially available field programmable gate array (FPGA). Using an FPGA allows for precise control of the time dependent microwave-dressing applied to a sample of trapped cold atoms. We test our microwave source by exciting Rabi oscillations in a Na spinor Bose-Einstein Condensate. We include, as supplements, the complete source code, parts… ▽ More We present a microwave source that is controlled by a commercially available field programmable gate array (FPGA). Using an FPGA allows for precise control of the time dependent microwave-dressing applied to a sample of trapped cold atoms. We test our microwave source by exciting Rabi oscillations in a Na spinor Bose-Einstein Condensate. We include, as supplements, the complete source code, parts lists, pin connection diagrams, and schematics to make it easy for any group to build and use this device. △ Less

Submitted 18 September, 2019; originally announced September 2019.

Journal ref: Rev. Sci. Instrum. 91, 023202 (2020)

Exploring co-sputtering of ZnO:Al and SiO2 for efficient electron-selective contacts on silicon solar cells

Authors: Sihua Zhong, Monica Morales-Masis, Mathias Mews, Lars Korte, Quentin Jeangros, Weiliang Wu, Mathieu Boccard, Christophe Ballif

Abstract: In recent years, considerable efforts have been devoted to developing novel electron-selective materials for crystalline Si (c-Si) solar cells with the attempts to simplify the fabrication process and improve efficiency. In this study, ZnO:Al (AZO) is co-sputtered with SiO2 to form AZO:SiO2 films with different SiO2 content. These nanometer-scale films, deposited on top of thin intrinsic hydrogena… ▽ More In recent years, considerable efforts have been devoted to developing novel electron-selective materials for crystalline Si (c-Si) solar cells with the attempts to simplify the fabrication process and improve efficiency. In this study, ZnO:Al (AZO) is co-sputtered with SiO2 to form AZO:SiO2 films with different SiO2 content. These nanometer-scale films, deposited on top of thin intrinsic hydrogenated amorphous silicon films and capped with low-work-function metal (such as Al and Mg), are demonstrated to function effectively as electron-selective contacts in c-Si solar cells. On the one hand, AZO:SiO2 plays an important role in such electron-selective contact and its thickness is a critical parameter, thickness of 2 nm showing the best. On the other hand, at the optimal thickness of AZO:SiO2, the open circuit voltage (VOC) of the solar cells is found to be relatively insensitive to either the work function or the band gap of AZO:SiO2. Whereas, regarding the fill factor (FF), AZO without SiO2 content exhibits to be the optimal choice. By using AZO/Al as electron-selective contact, we successfully realize a 19.5%-efficient solar cell with VOC over 700 mV and FF around 75%, which is the best result among c-Si solar cells using ZnO as electron-selective contact. Also, this work implies that efficient carrier-selective film can be made by magnetron sputtering method. △ Less

Submitted 7 February, 2019; originally announced February 2019.

Temporal Resolution of the RABBITT technique

Authors: M. Isinger, D. Busto, S. Mikaelsson, S. Zhong, C. Guo, P. Salières, C. L. Arnold, A. L'Huillier, M. Gisselbrecht

Abstract: One of the most ubiquitous techniques within attosecond science is the so-called Reconstruction of Attosecond Bursts by Interference of Two-Photon Transitions (RABBITT). Originally proposed for the characterization of attosecond pulses, it has been successfully applied to accurate determinations of time delays in photoemission. Here, we examine in detail, using numerical simulations, the effect of… ▽ More One of the most ubiquitous techniques within attosecond science is the so-called Reconstruction of Attosecond Bursts by Interference of Two-Photon Transitions (RABBITT). Originally proposed for the characterization of attosecond pulses, it has been successfully applied to accurate determinations of time delays in photoemission. Here, we examine in detail, using numerical simulations, the effect of the spatial and temporal properties of the light fields and of the experimental procedure on the accuracy of the method. This allows us to identify the necessary conditions to achieve the best temporal resolution in RABBITT measurements. △ Less

Submitted 17 December, 2018; originally announced December 2018.

Fano's propensity rule in angle-resolved attosecond pump-probe photoionization

Authors: David Busto, Jimmy Vinbladh, Shiyang Zhong, Marcus Isinger, Saikat Nandi, Sylvain Maclot, Per Johnsson, Mathieu Gisselbrecht, Anne L'Huillier, Eva Lindroth, Jan Marcus Dahlström

Abstract: In a seminal article, Fano predicts that absorption of light occurs preferably with increase of angular momentum. Here we generalize Fano's propensity rule to laser-assisted photoionization, consisting of absorption of an extreme-ultraviolet photon followed by absorption or emission of an infrared photon. The predicted asymmetry between absorption and emission leads to incomplete quantum interfere… ▽ More In a seminal article, Fano predicts that absorption of light occurs preferably with increase of angular momentum. Here we generalize Fano's propensity rule to laser-assisted photoionization, consisting of absorption of an extreme-ultraviolet photon followed by absorption or emission of an infrared photon. The predicted asymmetry between absorption and emission leads to incomplete quantum interference in attosecond photoelectron interferometry. It explains both the angular-dependence of the photoionization time delays and the delay-dependence of the photoelectron angular distributions. Our theory is verified by experimental results in Ar in the 20-40 eV range. △ Less

Submitted 24 May, 2019; v1 submitted 13 November, 2018; originally announced November 2018.

Journal ref: Phys. Rev. Lett. 123, 133201 (2019)

Time-frequency representations of autoionization dynamics in helium

Authors: D. Busto, L. Barreau, M. Isinger, M. Turconi, C. Alexandridi, A. Harth, S. Zhong, R. J. Squibb, D. Kroon, S. Plogmaker, M. Miranda, Á. Jiménez-Galán, L. Argenti, C. L. Arnold, R. Feifel, F. Martín, M. Gisselbrecht, A. L'Huillier, P. Salières

Abstract: Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the i… ▽ More Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wavepacket. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wavepackets emitted via the sp2+ and sp3+ resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build up of the wavepackets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels. △ Less

Submitted 15 December, 2017; v1 submitted 22 September, 2017; originally announced September 2017.

Photoionization in the time and frequency domain

Authors: M. Isinger, R. J. Squibb, D. Busto, S. Zhong, A. Harth, D. Kroon, S. Nandi, C. L. Arnold, M. Miranda, J. M. Dahlström, E. Lindroth, R. Feifel, M. Gisselbrecht, A. L'Huillier

Abstract: Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration ($10^{-18}$s) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses may raise serious issues in the interpretation of the experimental results and the comparison with detailed theor… ▽ More Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration ($10^{-18}$s) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses may raise serious issues in the interpretation of the experimental results and the comparison with detailed theoretical calculations. Here, we determine photoionization time delays in neon atoms over a 40 eV energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake up, where a second electron is left in an excited state, thus obtaining excellent agreement with theoretical calculations and thereby solving a puzzle raised by seven-year-old measurements. Our experimental approach does not have conceptual limits, allowing us to foresee, with the help of upcoming laser technology, ultra-high resolution time-frequency studies from the visible to the x-ray range. △ Less

Submitted 7 September, 2017; v1 submitted 6 September, 2017; originally announced September 2017.

Comments: 5 pages, 4 figures

The electromagnetic waves propagation in unmagnetized plasma media using parallelized finite-difference time-domain method

Authors: Lang-lang Xiong, Xi-min Wang, Song Liu, Zhi-yun Peng, Shuang-ying Zhong

Abstract: The finite-difference time-domain (FDTD) method has been commonly utilized to simulate the electromagnetic (EM) waves propagation in the plasma media. However, the FDTD method may bring about extra run-time on concerning computationally large and complicated EM problems. Fortunately, the FDTD method is easy to parallelize. Besides, GPU has been widely used for parallel computing due to its unique… ▽ More The finite-difference time-domain (FDTD) method has been commonly utilized to simulate the electromagnetic (EM) waves propagation in the plasma media. However, the FDTD method may bring about extra run-time on concerning computationally large and complicated EM problems. Fortunately, the FDTD method is easy to parallelize. Besides, GPU has been widely used for parallel computing due to its unique SPMD (Single Program Multiple Data) architecture. In this paper, we represent the parallel Runge-Kutta exponential time differencing scheme FDTD (RKETD) method for the unmagnetized plasma implemented on GPU. The detailed flowchart of parallel RKETD-FDTD method is described. The accuracy and acceleration performance of the proposed parallel RKETD-FDTD method implemented on GPU are substantiated by calculating the reflection and transmission coefficients for one-dimensional unmagnetized plasma slab. The results indicate that the numerical precision of the parallel RKETD-FDTD scheme is consistent with that of the code implemented on CPU. The computation efficiency is greatly improved compared with merely CPU-based serial RKETD-FDTD method. Moreover, the comparisons of the performance of CUDA-based GPU parallel program, OpenMP (Open Multi-Processing)-based CPU parallel program, and single-CPU serial program on the same host computer are done. Compared with the serial program, both parallel programs get good results, while GPU-based parallel program gains better result. △ Less

Submitted 12 April, 2018; v1 submitted 4 September, 2017; originally announced September 2017.

Comments: 12 pages,3 figures

Journal ref: Lang-lang Xiong, Xi-min Wang, Song Liu, Zhi-yun Peng, Shuang-ying Zhong, The electromagnetic waves propagation in unmagnetized plasma media using parallelized finite-difference time-domain method, Optik, Volume 166, August 2018, Pages 8-14

The first result on 76Ge neutrinoless double beta decay from CDEX-1 experiment

Authors: Li Wang, Qian Yue, KeJun Kang, JianPing Cheng, YuanJing Li, TszKing Henry Wong, ShinTed Lin, JianPing Chang, JingHan Chen, QingHao Chen, YunHua Chen, Zhi Deng, Qiang Du, Hui Gong, Li He, QingJu He, JinWei Hu, HanXiong Huang, TengRui Huang, LiPing Jia, Hao Jiang, HauBin Li, Hong Li, JianMin Li, Jin Li , et al. (48 additional authors not shown)

Abstract: We report the first result on Ge-76 neutrinoless double beta decay from CDEX-1 experiment at China Jinping Underground Laboratory. A mass of 994 g p-type point-contact high purity germanium detector has been installed to search the neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg*day has been analyzed. The wideband spectrum from 500… ▽ More We report the first result on Ge-76 neutrinoless double beta decay from CDEX-1 experiment at China Jinping Underground Laboratory. A mass of 994 g p-type point-contact high purity germanium detector has been installed to search the neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg*day has been analyzed. The wideband spectrum from 500 keV to 3 MeV was obtained and the average event rate at the 2.039 MeV energy range is about 0.012 count per keV per kg per day. The half-life of Ge-76 neutrinoless double beta decay has been derived based on this result as: T 1/2 > 6.4*10^22 yr (90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved. The possible methods to further decrease the background level have been discussed and will be pursued in the next stage of CDEX experiment. △ Less

Submitted 6 March, 2017; originally announced March 2017.

Comments: 8 pages, 8 figures

Journal ref: Sci. China-Phys. Mech. Astron. 60, 071011 (2017)

Plasmonic and Metamaterial Structures as Electromagnetic Absorbers

Authors: Yanxia Cui, Yingran He, Yi Jin, Fei Ding, Liu Yang, Yuqian Ye, Shoumin Zhong, Yinyue Lin, Sailing He

Abstract: Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic det… ▽ More Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on. △ Less

Submitted 22 April, 2014; originally announced April 2014.

Comments: 26 pages, 12 figures

Acoustic Invisibility in Turbulent Fluids

Authors: Xun Huang, Siyang Zhong

Abstract: Acoustic invisibility of a cloaking system in turbulent uids has been poorly understood. Here we show that evident scattering would appear in turbulent wakes owing to the submergence of a classical cloaking device. The inherent mechanism is explained using our theoretical model, which eventually inspires us to develop an optimized cloaking approach. Both the near- and far-field scatted fields are… ▽ More Acoustic invisibility of a cloaking system in turbulent uids has been poorly understood. Here we show that evident scattering would appear in turbulent wakes owing to the submergence of a classical cloaking device. The inherent mechanism is explained using our theoretical model, which eventually inspires us to develop an optimized cloaking approach. Both the near- and far-field scatted fields are examined using high order computational acoustic methods. The remarkably low scattering demonstrates the effectiveness of the proposed acoustic cloaking approach for turbulent uid cases. △ Less

Submitted 3 December, 2013; originally announced December 2013.

Comments: 6 pages, 4 figures in the attachment, but 3 Figures in the article

Use strong coupling strength to coherently preserve quantum entanglement

Authors: Guihua Tian, Shuquan Zhong

Abstract: The dynamics of two qubits ultra-strongly coupled with a quantum oscillator is investigated by the adiabatic approximation method. The evolution formula of the initial four Bell states are studied under the control mechanism of the coherent state of the quantum oscillator. The influential parameters for the preservation of the entanglement are the four parameters: the average number of the coheren… ▽ More The dynamics of two qubits ultra-strongly coupled with a quantum oscillator is investigated by the adiabatic approximation method. The evolution formula of the initial four Bell states are studied under the control mechanism of the coherent state of the quantum oscillator. The influential parameters for the preservation of the entanglement are the four parameters: the average number of the coherent state, the ultra-strong coupling strength, the ratio of two frequencies of qubit and oscillator, and the inter-interaction coupling of the two qubits. The novel results show that the appropriate choice of these parameters can enable this mechanism to be utilized to preserve the entanglement of the two qubits, which is initially in the state |I_0> of the four Bell states. We give two different schemes to choose the respective parameters to maintain the entangled state |I_0> almost unchanged. The results will be helpful for the quantum information process. △ Less

Submitted 24 September, 2013; originally announced September 2013.

Comments: 9 pages

First results on low-mass WIMP from the CDEX-1 experiment at the China Jinping underground Laboratory

Authors: W. Zhao, Q. Yue, K. J. Kang, J. P. Cheng, Y. J. Li, S. T. Lin, Y. Bai, Y. Bi, J. P. Chang, N. Chen, N. Chen, Q. H. Chen, Y. H. Chen, Y. C. Chuang, Z. Deng, C. Du, Q. Du, H. Gong, X. Q. Hao, H. J. He, Q. J. He, X. H. Hu, H. X. Huang, T. R. Huang, H. Jiang , et al. (54 additional authors not shown)

Abstract: The China Dark matter Experiment collaboration reports the first experimental limit on WIMP dark matter from 14.6 kg-day of data taken with a 994 g p-type point-contact germanium detector at the China Jinping underground Laboratory where the rock overburden is more than 2400 m. The energy threshold achieved was 400 eVee. According to the 14.6 kg-day live data, we placed the limit of N= 1.75 * 10^{… ▽ More The China Dark matter Experiment collaboration reports the first experimental limit on WIMP dark matter from 14.6 kg-day of data taken with a 994 g p-type point-contact germanium detector at the China Jinping underground Laboratory where the rock overburden is more than 2400 m. The energy threshold achieved was 400 eVee. According to the 14.6 kg-day live data, we placed the limit of N= 1.75 * 10^{-40} cm^{2} at 90% confidence level on the spin-independent cross-section at WIMP mass of 7 GeV before differentiating bulk signals from the surface backgrounds. △ Less

Submitted 8 August, 2013; v1 submitted 18 June, 2013; originally announced June 2013.

Comments: 5 pages, 5 figures

Journal ref: Physical Review D 88, 052004 (2013)

The CDEX-1 1 kg Point-Contact Germanium Detector for Low Mass Dark Matter Searches

Authors: Ke-Jun Kang, Qian Yue, Yu-Cheng Wu, Jian-Ping Cheng, Yuan-Jing Li, Yang Bai, Yong Bi, Jian-Ping Chang, Nan Chen, Ning Chen, Qing-Hao Chen, Yun-Hua Chen, You-Chun Chuang, Zhi Dend, Qiang Du, Hui Gong, Xi-Qing Hao, Qing-Ju He, Xin-Hui Hu, Han-Xiong Huang, Teng-Rui Huang, Hao Jiang, Hau-Bin Li, Jian-Min Li, Jin Li , et al. (51 additional authors not shown)

Abstract: The CDEX Collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold p-type point-contact germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-conta… ▽ More The CDEX Collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold p-type point-contact germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-contact p+ electrode and the outside n+ electrode make it possible to scan the lower energy range of less than 1 keV and at the same time to detect the higher energy range up to 3 MeV. The outputs from both p+ and n+ electrode may also provide a more powerful method for signal discrimination for dark matter experiment. Some key parameters, including energy resolution, dead time, decay times of internal X-rays, and system stability, have been tested and measured. The results show that the 1 kg point-contact germanium detector, together with its shielding system and electronics, can run smoothly with good performances. This detector system will be deployed for dark matter search experiments. △ Less

Submitted 2 May, 2013; originally announced May 2013.

Comments: 6 pages, 8 figures

Journal ref: Chinese Physics C, 2013, 37(12): 126002

Introduction of the CDEX experiment

Authors: Ke-Jun Kang, Jian-Ping Cheng, Jin Li, Yuan-Jing Li, Qian Yue, Yang Bai, Yong Bi, Jian-Ping Chang, Nan Chen, Ning Chen, Qing-Hao Chen, Yun-Hua Chen, Zhi Deng, Qiang Du, Hui Gong, Xi-Qing Hao, Hong-Jian He, Qing-Ju He, Xin-Hui Hu, Han-Xiong Huang, Hao Jiang, Jian-Min Li, Xia Li, Xin-Ying Li, Xue-Qian Li , et al. (39 additional authors not shown)

Abstract: Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground lab… ▽ More Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground laboratory CJPL is the deepest underground lab in the world and provides a very promising environment for direct observation of dark matter. The China Dark Matter Experiment (CDEX) experiment is going to directly detect the WIMP flux with high sensitivity in the low mass region. Both CJPL and CDEX have achieved a remarkable progress in recent two years. The CDEX employs a point-contact germanium semi-conductor detector PCGe whose detection threshold is less than 300 eV. We report the measurement results of Muon flux, monitoring of radioactivity and Radon concentration carried out in CJPL, as well describe the structure and performance of the 1 kg PCGe detector CDEX-1 and 10kg detector array CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of the CDEX-1, CDEX-10 and the future CDEX-1T detectors. △ Less

Submitted 3 March, 2013; originally announced March 2013.

Comments: 36pages,39 figures

Journal ref: Front. Phys., 2013,8(4):412-437

Ultrathin microwave absorbers made of mu-near-zero metamaterials

Authors: Shuomin Zhong, Sailing He

Abstract: In this paper, mu-near-zero (MNZ) metamaterials are utilized to achieve an ultrathin absorber with a thickness of only about one percent of the operating wavelength. The metamaterial absorber (MA) is made of double-layered metallic spiral arrays designed to have a large purely imaginary permeability at low microwave frequencies (~ 1.7 GHz). An absorption efficiency above 90% is demonstrated at ill… ▽ More In this paper, mu-near-zero (MNZ) metamaterials are utilized to achieve an ultrathin absorber with a thickness of only about one percent of the operating wavelength. The metamaterial absorber (MA) is made of double-layered metallic spiral arrays designed to have a large purely imaginary permeability at low microwave frequencies (~ 1.7 GHz). An absorption efficiency above 90% is demonstrated at illumination angles up to 60 degrees. A polarization-insensitive MA implemented by 2D isotropic metamaterials is also studied. Our designs have great application potential as compared with the traditional heavy and thick absorbers made of natural materials working at the same frequencies. △ Less

Submitted 27 September, 2012; originally announced September 2012.

Geophysical and geochemical constraints on geoneutrino fluxes from Earth's mantle

Authors: Ondřej Šrámek, William F. McDonough, Edwin S. Kite, Vedran Lekić, Steve Dye, Shijie Zhong

Abstract: Knowledge of the amount and distribution of radiogenic heating in the mantle is crucial for understanding the dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Although the flux of heat from the surface of the planet is robustly estimated, the contributions of radiogenic heating and secular cooling remain poorly def… ▽ More Knowledge of the amount and distribution of radiogenic heating in the mantle is crucial for understanding the dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Although the flux of heat from the surface of the planet is robustly estimated, the contributions of radiogenic heating and secular cooling remain poorly defined. Constraining the amount of heat-producing elements in the Earth will provide clues to understanding nebula condensation and planetary formation processes in early Solar System. Mantle radioactivity supplies power for mantle convection and plate tectonics, but estimates of mantle radiogenic heat production vary by a factor of more than 20. Recent experimental results demonstrate the potential for direct assessment of mantle radioactivity through observations of geoneutrinos, which are emitted by naturally occurring radionuclides. Predictions of the geoneutrino signal from the mantle exist for several established estimates of mantle composition. Here we present novel analyses, illustrating surface variations of the mantle geoneutrino signal for models of the deep mantle structure, including those based on seismic tomography. These variations have measurable differences for some models, allowing new and meaningful constraints on the dynamics of the planet. An ocean based geoneutrino detector deployed at several strategic locations will be able to discriminate between competing compositional models of the bulk silicate Earth. △ Less

Submitted 18 October, 2012; v1 submitted 3 July, 2012; originally announced July 2012.

Comments: 34 pages, 6 tables, 5 figures, 2 supplementary figures; revised version submitted to Earth Planet. Sci. Lett

Journal ref: Earth Planet. Sci. Lett., vol. 361, pp. 356-366, 2013

Circular Sound Wave Scattering Derivation for Acoustic Cloak Detection

Authors: Siyang Zhong, Xun Huang

Abstract: In this Letter we develop analytical formulations to describe sound scattering in lossless medium due to 2D circular wave incident on an acoustic cloak. A perfect acoustic cloak is reflectionless and can completely hide the cloaked object from any sound waves. However, the realization of a perfect acoustic cloak is difficult. Compared to plane wave, our analytic calculations show that circular wav… ▽ More In this Letter we develop analytical formulations to describe sound scattering in lossless medium due to 2D circular wave incident on an acoustic cloak. A perfect acoustic cloak is reflectionless and can completely hide the cloaked object from any sound waves. However, the realization of a perfect acoustic cloak is difficult. Compared to plane wave, our analytic calculations show that circular wave from an annular line source generates distinct scattering patterns from an imperfect cloak design. Large modification in reflection directivities can be observed if the focal point of the incident wavefront is slightly customized. Hence, our work might find applications in acoustic cloak detection, which should have significant impact on cloak design and defense. △ Less

Submitted 4 May, 2012; originally announced May 2012.

Comments: 9 pages, 3 figures

A New Integral Equation for the Spheroidal equations in case of m equal 1

Authors: Guihua Tian, Shuquan Zhong

Abstract: The spheroidal wave functions are investigated in the case m=1. The integral equation is obtained for them. For the two kinds of eigenvalues in the differential and corresponding integral equations, the relation between them are given explicitly. Though there are already some integral equations for the spheroidal equations, the relation between their two kinds of eigenvalues is not known till now.… ▽ More The spheroidal wave functions are investigated in the case m=1. The integral equation is obtained for them. For the two kinds of eigenvalues in the differential and corresponding integral equations, the relation between them are given explicitly. Though there are already some integral equations for the spheroidal equations, the relation between their two kinds of eigenvalues is not known till now. This is the great advantage of our integral equation, which will provide useful information through the study of the integral equation. Also an example is given for the special case, which shows another way to study the eigenvalue problem. △ Less

Submitted 5 January, 2012; originally announced January 2012.