arXiv subjects

D. Wang

Publications and source records attributed to D. Wang.

At least 19 recordsLinked to original sources

arXiv2026

Guided spin wave in monolayer CrSBr: Localization and spin-orbit coupling from dipolar field

Spin-wave spectrum of monolayer CrSBr waveguides was studied by numerically diagonalizing the Bogoliubov-de Gennes Hamiltonian derived from linearising the Landau-Lifshitz-Gilbert equation. In contrast to its short-range counterparts, the long-range dipolar field acts statically as a confining potential for spin wave, while the dynamic part couples the spin and orbit degrees of freedom, thus giving rise to spin-orbit coupling for spin wave. Due to the inversion symmetry of the Hamiltonian and the spinor structure of the wave function, spin-wave eigenstates form doublets with definite parity. Micromagnetic simulation tallies well with numerical calculation. Our study on spin-wave eigenstates in CrSBr waveguides sheds light on the nature of exchange-dipole spin wave in ferromagnetic slabs. We confirm particularly that the robustness of the Damon-Eshbach mode is not derived from topology, but rather from the static dipolar field. Moreover, a thorough knowledge on spin wave in monolayer CrSBr itself represents a step forward to understanding the more complicated antiferromagnetic resonance in bulk CrSBr.

cond-mat.mes-hall↗

arXiv2025

Rational regulation strategies of interstitial localized electrons in electride: A density functional theory study

As a class of electron-rich materials, electrides demonstrate promising applications in many fields. However, the required high pressure restricts the practical applications to some extent. This study reveals that the unique feature of electride, i.e., the localization of interstitial electrons, can be greatly enhanced and tuned by self-defective doping, applying tensile/compressive stress, or shear stress. Moreover, the requirement of orbital orthogonality between the valence and core electron wave functions, as well as the Pauli exclusion principle, should be the driven force for the electron interstitial localization; and the exertion of external pressure modifies the available space to accommodate the electronic wave functions, thus enhances the interstitial localization. These discoveries lay down the ground for searching for promising electrides that are practicable at ambient conditions.

cond-mat.mtrl-sci↗

arXiv2025

Photoelectric detection of single spins in diamond by optically controlled discharge of long-lived trap states

Electrical detection methods for solid-state spins are attractive for quantum technologies, being readily chip-scalable and not subject to the small photon budgets of single emitters. However, realising electrical spin readout in wide-bandgap materials with similar fidelity and bandwidth to optical approaches remains challenging. Here, we introduce a photoelectrical spin readout scheme that detects spin information stored long-term as trapped electrical charges. Using nitrogen-vacancy (NV) centres in diamond as a model system, spin-dependent photoionisation generates charge carriers that are stored in long-lived trap states at a diamond-metal Schottky junction. On-demand illumination of the junction under electrical bias releases stored charge, yielding a photocurrent transient proportional to the amount of trapped charge and hence spin state. Spin readout after coherent control of single NVs is demonstrated using charge readout in a protocol we call charge-capture detected magnetic resonance (CCDMR), and we use charge-based imaging to identify charge carrier generation and trapping processes. Our results establish CCDMR as a new technique for solid-state spin qubit readout, combining attaractive features of electrical detection with the stability of long-lived charge traps in wide-bandgap materials.

quant-ph↗

arXiv2025

The CCOR Compact Coronagraphs for the Geostationary Operational Environmental Satellite-19 (GOES-19) and the Space Weather Follow On (SWFO) Missions

The CCOR Compact Coronagraph is a series of two operational solar coronagraphs sponsored by the National Oceanic and Atmospheric Administration (NOAA). They were designed, built, and tested by the U.S. Naval Research Laboratory (NRL). The CCORs will be used by NOAA's Space Weather Prediction Center to detect and track Coronal Mass Ejections (CMEs) and predict the Space Weather. CCOR-1 is on board the Geostationary Operational Environmental Satellite -U (GOES-U, now GOES-19/GOES-East). GOES-U was launched from Kennedy Space Flight Center, Florida, on 25 June 2024. CCOR-2 is on board the Space Weather Follow On at Lagrange point 1 (SWFO-L1). SWFO-L1 is scheduled to launch in the fall of 2025. SWFO will be renamed SOLAR-1 once it reaches L1. The CCORs are white-light coronagraphs that have a field of view and performance similar to the SOHO LASCO C3 coronagraph. CCOR-1 FOV spans from 4 to 22 Rsun, while CCOR-2 spans from 3.5 to 26 Rsun. The spatial resolution is 39 arcsec for CCOR-1 and 65 arcsec for CCOR-2. They both operate in a band-pass of 470 - 740 nm. The synoptic cadence is 15 min and the latency from image capture to the forecaster on the ground is less than 30 min. Compared to past generation coronagraphs such as the Large Angle and Spectrometric Coronagraph (LASCO), CCOR uses a compact design; all the solar occultation is done with a single multi-disk external occulter. No internal occulter is used. This allowed a substantial reduction in size and mass compared to SECCHI COR-2, for example, but with slightly lower signal-to-noise ratio. In this article, we review the science that the CCORs will capitalize on for the purpose of operational space weather prediction. We give a description of the driving requirements and accommodations, and provide details on the instrument design. In the end, information on ground processing and data levels is provided.

astro-ph.IM↗

arXiv2025

Measuring short-range correlations and quasi-elastic cross sections in A(e,e') at x>1 and modest Q$^2$

We present results from the Jefferson Lab E08-014 experiment, investigating short-range correlations (SRC) through measurements of inclusive quasi-elastic scattering from $^2$H, $^3$He, $^4$He, $^{12}$C, $^{40}$Ca, and $^{48}$Ca. The kinematics were selected to isolate scattering from SRCs, yielding a plateau in the A/$^2$H cross-section ratios due to the universal two-body structure of the 2N-SRCs in light and heavy nuclei. We observe approximate plateaus in the A/$^2$H ratios and provide the first extractions of the A/$^2$H ratio for $^{40}$Ca and $^{48}$Ca. We also examine the A/$^3$He ratio, aiming to identify three-nucleon SRCs (3N-SRCs). Following the approach for isolating 2N-SRCs, searching for 3N-SRC dominance involved measuring the A/$^3$He cross section ratio at modest-to-large $Q^2$ values and looking for a plateau ratios for $x \gtorder 2.5$. This was not observed in the data, and in fact increasing $Q^2$ values moved the data \textit{further away} from the predicted plateau. We show here that, when analyzed in terms of the struck nucleon's light-cone momentum, the data exhibited the expected trend, progressively approaching the predicted 3N-SRC plateau. These observations suggest that future measurements at higher energies may facilitate a definitive isolation and identification of 3N-SRCs.

nucl-ex↗

arXiv2025

He-Mg compounds and helium-driven nonmetal transition in metallic magnesium

The polymorphism and mechanism of helium compounds is crucial for understanding the physical and chemical nature of He-bearing materials under pressures. Here, we predict two new types of He-bearing compounds, MgHe and MgnHe (n = 6, 8, 10, 15, 18), being formed above 750 GPa by unbiased ab initio structure search. An unexpected bandgap is opened up in MgHe at as low as around 200 GPa. This is the first case of noble gas driven metal-nonmetal transition in all elements. The same mechanism is demonstrated also being applicable to other metallic elements, and making beryllium transform into a non-metallic state, a triumph that is impossible otherwise. Furthermore, the stability of the simple cubic phase of Mg (Mg-sc) is greatly enhanced by mixing with He, which lowers the critical pressure of pure Mg-sc from about 1.1 TPa down to 750 GPa to form ordered substitutional alloying phase of MgnHe on a simple cubic lattice of Mg. This is the first report on Mg-based noble gas substitutional alloy, in sharp contrast to the conventional wisdom that He preferring interstitial sites. The observed striking influences of He demonstrate the rich physics and chemistry of He-bearing compounds under ultra-high pressures.

cond-mat.mtrl-sci↗

arXiv2025

Simultaneous Superconducting and Topological Properties in Mg-Li Electrides at High Pressures

Electrides as a unique class of emerging materials exhibit fascinating properties and hold important significance for understanding the matter under extreme conditions, which is characterized by valence electrons localized into the interstitial space as quasi-atoms (ISQs). In this work, using crystal structure prediction and first-principles calculations, we identified seven stable phases of Mg-Li that are electride with novel electronic properties under high pressure. Among them, MgLi10 is a semiconductor with a band gap of 0.22 eV; and Pm-3m MgLi is superconductor with a superconducting transition temperature of 22.8 K. The important role played by the localization degree of ISQ in the superconducting transition temperature of these electrides is revealed by systematic comparison of Mg-Li with other Li-rich electride superconductors. Furthermore, we proved that Pm-3m MgLi and Pnma MgLi also have distinct topological behavior with metallic surface states and the non-zero $Z_2$ invariant. The simultaneous coexistence of superconductivity, electronic band topology and electride property in the same structure of Pm-3m MgLi and Pnma MgLi demonstrates the feasibility of realizing multi-quantum phases in a single material, which will stimulate further research in these interdisciplinary fields.

cond-mat.mtrl-sci↗

arXiv2024

Flexible strained membranes of multiferroic TbMnO3

The multiferroic properties of TbMnO3 demonstrate high versatility under applied pressure, making the material potentially suitable for use in flexible electronics. Here, we report on the preparation of elastic freestanding TbMnO3 membranes with dominant (001) or (010) crystallographic out-of-plane orientation. Membranes with thickness of 20 nm display orthorhombic bulk-like relaxed lattice parameters with strong suppression of twinning for the (010) oriented membranes. Strain in flexible membranes was tuned by using a commercial strain cell device and characterized by Raman spectroscopy. The B1g out-of-phase oxygen-stretching mode, representative for the Mn-O bond distance, systematically shifts to lower energy with increasing strain (epsilon{max} ~ 0.5 %). The flexibility and elastic properties of the membranes allow for specific manipulation of the multiferroic state by strain, whereas the choice of the crystallographic orientation gives possibility for an in- or out-of-plane electric polarization.

cond-mat.mtrl-sci↗

arXiv2023

Latent Space Inference For Spatial Transcriptomics

In order to understand the complexities of cellular biology, researchers are interested in two important metrics: the genetic expression information of cells and their spatial coordinates within a tissue sample. However, state-of-the art methods, namely single-cell RNA sequencing and image based spatial transcriptomics can only recover a subset of this information, either full genetic expression with loss of spatial information, or spatial information with loss of resolution in sequencing data. In this project, we investigate a probabilistic machine learning method to obtain the full genetic expression information for tissues samples while also preserving their spatial coordinates. This is done through mapping both datasets to a joint latent space representation with the use of variational machine learning methods. From here, the full genetic and spatial information can be decoded and to give us greater insights on the understanding of cellular processes and pathways.

cs.LG↗

arXiv2023

Efficient InGaN-based Red Light-Emitting Diodes by Modulating Trench Defects

Trench defects in multi-quantum wells (MQWs) have been considered as flawed structures that severely degrade the internal quantum efficiency of light-emitting diodes (LEDs) in the past. In this research, trench defects are innovatively modulated into the structure to enhance the efficiency of red InGaN LEDs. Specifically, dual-color MQWs structures are grown with green MQWs at the bottom and red MQWs at the top. When high-density trench defects are introduced into the green MQWs, the upper red MQWs exhibit a significant wavelength redshift of 68 nm and approximately 6-fold luminescence enhancement compared to those without trench defects. The wavelength redshift is attributed to the increased indium incorporation due to the strain relaxation effect of trench defects. Moreover, the luminescence enhancement originates from the strong emission of the red MQWs inside trench defects. The mechanisms behind the superior luminescent properties of red MQWs within trench defects are explored in detail. Red InGaN LEDs with an internal quantum efficiency of 16.4% are achieved by modulating the trench defects. The method of achieving InGaN-based red emission by introducing trench defects is simple and reproducible, requiring no additional substrate designs. This research provides a novel pathway toward achieving high-efficiency red InGaN LEDs.

cond-mat.mtrl-sci↗

arXiv2023

On the Formation of Eccentric Millisecond Pulsars by Accretion-induced Collapse of Massive White Dwarfs

The millisecond pulsar(MSP) is believed to be an old neutron star(NS) having undergone spin-up by the accreting material from the donor. Whereas, the discovery of eccentric millisecond pulsars (eMSPs) in the Galactic field challenges such a scenario producing MSP-white dwarf (WD) only in the circular orbit. As orbital periods and companion mass of these eMSPs are located in a narrow range, a reasonable postulation is that they have the same origin. Although many models have been proposed to interpret their origin, however, the origin of the narrow range of the orbital period is still an open question. The accretion-induced collapse(AIC) of the ONe WD is considered to be an important pathway to form MSP, which was expected to result in the formation of MSP in the circular orbit due to tidal circularization. Here we revisited this scenario by the binary population synthesis including the specific circularization calculation. Our results indicate that binaries with insufficient circularization in this scenario can evolve into the eMSPs. The narrow initial binary parameters required by insufficient circularization can naturally account for the narrow range of the orbital period. Although the evolution of WD's AIC process has not been well understood, the characteristic of a narrow range in the orbital period of eMSPs can still set constraints on the physics of their evolution.

astro-ph.SR↗

arXiv2023

Multiple-Step Quantized Triplet STDP Implemented with Memristive Synapse

As an extension of the pairwise spike-timing-dependent plasticity (STDP) learning rule, the triplet STDP is provided with greater capability in characterizing the synaptic changes in the biological neural cell. In this work, a novel mixed-signal circuit scheme, called multiple-step quantized triplet STDP, is designed to provide a precise and flexible implementation of coactivation triplet STDP learning rule in memristive synapse spiking neural network. The robustness of the circuit is greatly improved through the utilization of pulse-width encoded weight modulation signals. The circuit performance is studied through the simulations which are carried out in MATLAB Simulink & Simscape, and assessment is given by comparing the results of circuits with the algorithmic approaches.

eess.SY↗

arXiv2023

Implementation of Multiple-Step Quantized STDP Based on Novel Memristive Synapses

Memristors have been widely studied as artificial synapses in neuromorphic circuits, due to their functional similarity with biological synapses, low operating power, and high integration density. In this work, a memristive synapse, composed of four memristors and two resistors, for SNN is designed and utilized for a neuron circuit implementing the robust spike-timing dependent plasticity learning. The synapse can be either excitatory or inhibitory by rationally arranging the resistors in the circuit. This is the first of its kind, enabling Hebbian and anti-Hebbian training without requiring additional processing of neural signals. Then, a neuron circuit is designed based on the proposed synapses. The robustness and compatibility of this neuron circuit are greatly enhanced by employing the clock-based square-wave pulsed to transmit spikes and modulate the synaptic weight. To study the performance of proposed synapses and circuit, simulations based on behavior models are carried out in the MATLAB Simulink and Simscape. Specially, a memristor model with balanced flexibility, efficiency, convergence, and emulation performance, is developed through including the nonlinear Joule effect. Using this memristor model in pattern learning, the influence of weak signal-induced weight variation on circuit performance can be rigorously assessed. This proposed circuit could give some inspiration for combining the analog memristive synapse and leaky integrate-and-fire neuron with digital control units, prompting their development as edge computing devices.

cs.ET↗

arXiv2023

Local and global measures of the shear moduli of jammed disk packings

Strain-controlled isotropic compression gives rise to jammed packings of repulsive, frictionless disks with either positive or negative global shear moduli. We carry out computational studies to understand the contributions of the negative shear moduli to the mechanical response of jammed disk packings. We first decompose the ensemble-averaged, global shear modulus as $\langle G\rangle = (1-{\cal F}_-) \langle G_+ \rangle + {\cal F}_- \langle G_-\rangle$, where ${\cal F}_-$ is the fraction of jammed packings with negative shear moduli and $\langle G_+\rangle$ and $\langle G_-\rangle$ are the average values from packings with positive and negative moduli, respectively. We show that $\langle G_+\rangle$ and $\langle|G_-|\rangle$ obey different power-law scaling relations above and below $pN^2 \sim 1$. We then calculate analytically that ${\cal P}(G)$ is a Gamma distribution in the $pN^2 \ll 1$ limit. As $pN^2$ increases, the skewness of ${\cal P}(G)$ decreases and ${\cal P}(G)$ becomes a skew-normal distribution with negative skewness in the $pN^2 \gg 1$ limit. We also partition jammed disk packings into subsystems using Delanunay triangulation of the disk centers to calculate local shear moduli. We show that the local shear moduli defined from groups of adjacent triangles can be negative even when $G > 0$. The spatial correlation function of local shear moduli $C({\vec r})$ displays weak correlations for $pn_{\rm sub}^2 < 10^{-2}$, where $n_{\rm sub}$ is the number of particles within each subsystem. However, $C({\vec r})$ begins to develop long-ranged spatial correlations with four-fold angular symmetry for $pn_{\rm sub}^2 \gtrsim 10^{-2}$.

cond-mat.soft↗

arXiv2022

Measurement of the mass and width of the $\Lambda_c(2625)^+$ and the branching ratios of $\Lambda_c(2625)^+ \to \Sigma_c^{0}\pi^{+}$ and $\Lambda_c(2625)^+ \to \Sigma_c^{++}\pi^{-}$

Using the entire data sample of $980\,\textrm{fb}^{-1}$ collected with the Belle detector operating at the KEKB asymmetric-energy collider, we report the measurement of the mass, width, and the relative branching ratios of the $\Lambda_c(2625)^+$ charmed baryon. The mass difference between $\Lambda_c(2625)^+$ and $\Lambda_c^+$ is measured to be $M(\Lambda_c(2625)^{+}) - M(\Lambda_c^{+}) = 341.518 \pm 0.006 \pm 0.049\ \mathrm{MeV}/\mathit{c}^2$. The upper limit on the width is measured to be $\Gamma(\Lambda_c(2625)^+) < 0.52\,\mathrm{MeV}/\textit{c}^2$ at 90\% credibility level. Based on a full Dalitz plot fit, branching ratios with respect to the mode $\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^+ \pi^-$ are measured to be $\frac{\mathcal{B}(\Lambda_c(2625)^+ \to \Sigma_c^{0} \pi^{+})} {\mathcal{B}(\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^{+} \pi^{-})} = (5.19 \pm 0.23 \pm 0.40) \%$ and $\frac{\mathcal{B}(\Lambda_c(2625)^+ \to \Sigma_c^{++} \pi^{-})} {\mathcal{B}(\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^{+} \pi^{-})} = (5.13 \pm 0.26 \pm 0.32) \%$. These measurements can be used to further constrain the parameters of the underlying theoretical models.

hep-ex↗

arXiv2022

Strain driven antiferromagnetic exchange interaction in SrMnO$_3$ probed by phase shifted Spin Hall magnetoresistance

Multiferroics have found renewed interest in topological magnetism and for logic-in-memory applications. Among them, SrMnO$_{3}$, possessing strong magnetoelectric coupling is gaining attention for the design of coexisting magnetic and polar orders upon straining. Here we demonstrate antiferromagnetic exchange interactions in strained SMO thin films extracted from a new feature in the phase response of Spin Hall magnetoresistance, which has not been explored in earlier works, such as in magnetic insulators. We explain our findings with a model that incorporates magnetic anisotropy along [110] direction, corroborates with DFT studies and is consistent with the direction of ferroelectric polarization in SrMnO$_{3}$. The fundamental insights obtained from our studies establishes the potential of this material in magnetoelectrically coupled devices for different logic and memory applications.

cond-mat.mtrl-sci↗

arXiv2022

Possible tidal dissipation in millisecond pulsar binaries

The post-Keplerian(PK) parameters inferred from pulsar timing provide a convenient way to test Einstein's general theory of relativity. However, before obtaining a pure orbital decay $\dot{P}_b$ induced by gravitational wave radiation, which is one of the PK parameters, a number of factors need to be accounted for carefully. The effect of tidal dissipation on $\dot{P}_b$ has been thought of as negligible. Here, we investigate the data for possible effects of tidal dissipation on $\dot{P}_b$. The possibility of the tidal dissipation as a contributor to $\dot{P}_b$ in a large sample of millisecond pulsar binaries is investigated in detail. We collected a large sample of pulsar binaries with measured $\dot{P}_b$. All of the systems are millisecond pulsars. The residual $\dot{P}^{Res}_b$ of these systems was obtained by subtracting the three normal effects, that is to say the effect of Shklovskii, line-of-sight acceleration, and gravitational radiation. Assuming that tidal dissipation is responsible for such a residual $\dot{P}^{Res}_b$, the tidal parameters of these systems can be calculated and compared with the tidal models. The residual $\dot{P}^{Res}_b$ is distributed over the half positive and half negative. The dynamical tidal model can explain the residual $\dot{P}_b$ of millisecond pulsar-white dwarf binaries. And the Love number of the main-sequence companion of \object{PSR J1227-4853} can be derived as a reasonable value $k_2=0.177^{+0.098}_{-0.058}$ with the equilibrium tidal model. Those results are compatible with the scenario of tidal dissipation. Additionally, a weak correlation between the tidal parameter and orbital period is revealed, likely originating in the tidal process of the recycled stage which is worthy of further investigation.

astro-ph.HE↗

arXiv2022

Snowmass 2021 White Paper on Upgrading SuperKEKB with a Polarized Electron Beam: Discovery Potential and Proposed Implementation

Upgrading the SuperKEKB electron-positron collider with polarized electron beams opens a new program of precision physics at a center-of-mass energy of 10.58 GeV. This white paper describes the physics potential of this `Chiral Belle' program. It includes projections for precision measurements of $\sin^2\theta_W$ that can be obtained from independent left-right asymmetry measurements of $e^+e^-$ transitions to pairs of electrons, muons, taus, charm and b-quarks. The $\sin^2\theta_W$ precision obtainable at SuperKEKB will match that of the LEP/SLC world average, but at the centre-of-mass energy of 10.58 GeV. Measurements of the couplings for muons, charm, and $b$-quarks will be substantially improved and the existing $3\sigma$ discrepancy between the SLC $A_{LR}$ and LEP $A_{FB}^b$ measurements will be addressed. Precision measurements of neutral current universality will be more than an order of magnitude more precise than currently available. As the energy scale is well away from the $Z^0$-pole, the precision measurements will have sensitivity to the presence of a parity-violating dark sector gauge boson, $Z_{\rm dark}$. The program also enables the measurement of the anomalous magnetic moment $g-2$ form factor of the $\tau$ to be made at an unprecedented level of precision. A precision of $10^{-5}$ level is accessible with 40~ab$^{-1}$ and with more data it would start to approach the $10^{-6}$ level. This technique would provide the most precise information from the third generation about potential new physics explanations of the muon $g-2$ $4\sigma$ anomaly. Additional $\tau$ and QCD physics programs enabled or enhanced with having polarized electron beams are also discussed in this White Paper. This paper includes a summary of the path forward in R&D and next steps required to implement this upgrade and access its exciting discovery potential.

physics.acc-ph↗