arXiv subjects

Dong Wu

Publications and source records attributed to Dong Wu.

At least 19 recordsLinked to original sources

arXiv2026

Sublattice-resolved coherent phonon dynamics in charge density waves

Phonons govern fundamental material properties and play a central role in various electronic phase transitions. Coherent driving of specific phonon modes enables on-demand phase control, motivating sublattice-resolved identification of real-space phonon motions. Yet experimentally resolving these motions remains challenging, limiting precise phonon-based control. Here, we introduce a dynamical protocol to track element-resolved phonon dynamics in the charge density wave material EuTe4, in which the dominant Te-sublattice charge order is accompanied by a previously unreported Eu-sublattice component. We leverage the elemental selectivity of time-resolved resonant X-ray scattering to reveal three coherent phonon modes with distinct sublattice character, thereby disentangling Eu- and Te-dominated lattice dynamics, in good agreement with theoretical calculations of the phonon eigenvectors. This time-domain approach, which surpasses the energy-resolution limits of conventional frequency-domain inelastic scattering, provides a broadly applicable framework for decomposing coherent phonons in multi-element materials, which is crucial for the targeted control of phases of matter.

cond-mat.mtrl-sci↗

arXiv2026

Temperature-driven sodium-ion dynamical-to-static crossover in the zig-zag ordered phase of Na$_{0.5}$CoO$_2$

We employ polarization-resolved Raman spectroscopy combined with first-principles calculations to study the sodium-ion lattice dynamics in a sodium zig-zag ordered cobaltate compound Na$_{0.5}$CoO$_2$. We detect two sodium phonon modes for the first time, and their mode frequencies are consistent with first-principles phonon calculations based on an orthorhombic unit cell. We find that they appear below around $T^*\sim300\pm50$K with large linewidth broadening, much lower than the sodium zig-zag ordering temperature $T_\text{S}\sim460$K, and then narrow at lower temperatures. We interpret the sodium-phonon anomalies occurring at $T^*$ as a dynamical-to-static crossover involving mainly the motion of sodium ions. Our results suggest that the gradual freezing of the sodium ions and the well-defined static sodium-zigzag order below $T^*$ set the stage for the emergent electronic and magnetic orders in the CoO$_2$ layer of Na$_{0.5}$CoO$_2$.

cond-mat.mtrl-sci↗

arXiv2026

Coherent seeding and control of dynamical ferroelectricity by phonon anharmonicity

Optical control of quantum materials has progressed along two separate directions: creating non-equilibrium states inaccessible at equilibrium, and coherently controlling ultrafast dynamics with multi-pulse protocols. Ferroelectricity is especially attractive in this context because its order parameter, macroscopic polarization, directly links inversion-symmetry breaking to functional response. Yet light-induced ferroelectricity has so far been confined to quantum paraelectrics near the ferroelectric instability, where critical fluctuations obscure the formation of a homogeneous ferroelectric state and complicate its deterministic coherent control. Unifying these capabilities -- preparing a symmetry-broken state and then coherently steering its functionality -- remains a central challenge. Here we show that intense terahertz excitation of a soft phonon mode induces a ferroelectric state in centrosymmetric PbTe, a thermoelectric material with strong lattice anharmonicity but no ferroelectric transition at finite temperature. The light-induced symmetry-broken state can be realized up to about 100 K, without relying on local dipolar fluctuations. Experiment and theory together reveal that terahertz-driven anharmonic coupling between degenerate transverse optical phonons underlies this ferroelectric induction. Furthermore, we demonstrate coherent amplification and suppression of the induced polarization via a double-pulse-excitation protocol. These results establish terahertz-driven anharmonic mode coupling as a general strategy for controlling mode-mediated functionalities in quantum materials, opening a route to ultrafast information processing.

cond-mat.mtrl-sci↗

arXiv2026

Probing kinetic enhancement of fusion reactivity in turbulent hot spots

Traditionally, fusion reactivity in thermonuclear plasmas has been calculated by assuming a local Maxwellian ion distribution. However, recent theoretical work [Phys. Rev. Lett. 135, 155101 (2025)] suggests that turbulence in plasmas can generate non-Maxwellian tail distributions, thereby enhancing reactivity. In this paper, we investigate this effect through numerical simulations of a sinusoidal shear flow. By comparing steady-state distributions obtained with the Bhatnagar-Gross-Krook (BGK) and Fokker-Planck (FP) collision operators, respectively, we demonstrate that the BGK model overestimates the reactivity enhancement while the FP operator gives a much more modest enhancement that is nearly halved under typical ICF parameters. Particle-in-cell (PIC) simulations incorporating nuclear reactions are also conducted, which reveal that the combined effects of preferential ion heating during shear flow dissipation and tail enhancement can even amplify the reactivity enhancement to be larger than the steady-state prediction.

physics.plasm-ph↗

arXiv2026

Room-temperature multistage metastability in a moir\'e superstructure

Metastability is fundamental not only to phase ordering and transitions, but also to a broad range of modern technologies, from memory devices to metallic glasses. In condensed-matter physics, charge density waves (CDWs) offer versatile platforms for accessing metastable states due to their sensitivity to external stimuli. However, most metastable CDW states are stabilized only at low temperatures, limiting their practical utility. In this study, we report the observation of electrically driven, room-temperature, nonvolatile metastable states in the bulk form of EuTe$_4$, a recently discovered compound that hosts an innate moir\'e superlattice characterized by the stacking of incommensurate monolayer and bilayer CDWs. Systematic transport measurements reveal discrete resistivity plateaus and strong electric-field sensitivity, with a large number of metastable states readily induced across a wide temperature window within a giant hysteresis loop, making them well-suited for high-temperature, multi-bit memory applications. By integrating photoemission spectroscopy, diffraction, and in-situ transport measurements, we uncover that these metastable states do not stem from conventional mechanisms such as the emergence of new ordered phases or changes in incommensurate periodicity. Instead, they are characterized by a suppression of the original CDW amplitude and a reduction in correlation length, pointing to a unique electric-field-induced switching of out-of-plane CDW phases in the moir\'e superstructure. Our findings not only provide critical insights into metastable phenomena in moir\'e systems with stacked electronic orders but also establish EuTe$_4$ as a promising platform for developing room-temperature, multi-bit memory devices.

cond-mat.str-el↗

arXiv2026

Online3R: Online Learning for Consistent Sequential Reconstruction Based on Geometry Foundation Model

We present Online3R, a new sequential reconstruction framework that is capable of adapting to new scenes through online learning, effectively resolving inconsistency issues. Specifically, we introduce a set of learnable lightweight visual prompts into a pretrained, frozen geometry foundation model to capture the knowledge of new environments while preserving the fundamental capability of the foundation model for geometry prediction. To solve the problems of missing groundtruth and the requirement of high efficiency when updating these visual prompts at test time, we introduce a local-global self-supervised learning strategy by enforcing the local and global consistency constraints on predictions. The local consistency constraints are conducted on intermediate and previously local fused results, enabling the model to be trained with high-quality pseudo groundtruth signals; the global consistency constraints are operated on sparse keyframes spanning long distances rather than per frame, allowing the model to learn from a consistent prediction over a long trajectory in an efficient way. Our experiments demonstrate that Online3R outperforms previous state-of-the-art methods on various benchmarks. Project page: https://shunkaizhou.github.io/online3r-1.0/

cs.CV↗

arXiv2026

Phase-locked phonon laser enhanced ultra-weak force measurement

Optically levitated micro- and nanoparticles are an ideal optomechanical platform for precision measurements, particularly enabling the detection of ultraweak forces. Nevertheless, quantum backaction and inherent instabilities induced by the trapping laser fundamentally restrict further improvements in force sensitivity and resolution. To circumvent these bottlenecks, we actively drive the levitated nanoparticle's mechanical motion in a phase-locked phonon laser mode and integrate a carrier-modulation measurement architecture to enhance force sensing capabilities. The stable and high-amplitude oscillation of the phonon laser allows for the robust trapping under 1 mW-level laser power, which in turn reduces the force noise to 4.0(3)*10^-22 N/Hz^1/2. Furthermore, by using phase-locked phonon laser, the measurement system achieves active stabilization and extended coherence time with the measured signal to 12,500 seconds, realizing a measurement resolution of 8(4)*10^-24 N with a sensitivity of 9.3(7)*10^-22 N/Hz^1/2 under a loaded force. These results establish the phonon laser as a low-noise, long-coherence-time, self-stabilizing platform for precision measurements, as well as in quantum and fundamental physics tests.

physics.optics↗

arXiv2026

Multimodal Terahertz Spectroscopy of the Pairing Symmetry and Normal-State Pseudogap in (La,Pr)$_3$Ni$_2$O$_7$ Films

The discovery of ambient-pressure superconductivity in compressively strained (La,Pr)$_3$Ni$_2$O$_7$ thin films has intensified efforts to identify the pairing mechanism. However, the symmetry of the superconducting order parameter and the character of the normal state remain unsettled. Here we combine bulk-sensitive terahertz (THz) time-domain spectroscopy with THz third-harmonic generation to present spectroscopic insights into these issues. Linear THz spectroscopy reveals a bulk superconducting response in the (La,Pr)$_3$Ni$_2$O$_7$ films, evidenced by the suppression of low-frequency spectral weight below the onset critical temperature, $T_\mathrm{c}^{\mathrm{onset}}$. A weak coherence peak near $T_\mathrm{c}^{\mathrm{onset}}$, together with substantial residual low-frequency conductivity as $T\to 0$, is consistent with disordered $s_{\pm}$-wave pairing. In the nonlinear regime, the third-harmonic signal rises sharply on cooling through $T_\mathrm{c}^{\mathrm{onset}}$, providing an independent signature of the transition. Strikingly, the nonlinear response persists above $T_\mathrm{c}^{\mathrm{onset}}$, pointing to either disorder-enhanced nonlinearity or a distinct correlated normal state. Motivated by angle-resolved photoemission spectroscopy on similarly grown films that identifies a comparable temperature scale, we associate the anomalous normal-state terahertz nonlinearity with a pseudogap. These results establish (La,Pr)$_3$Ni$_2$O$_7$ as a bulk superconductor with $s_{\pm}$-like pairing that coexists with, and may compete with, a distinct ordered state, providing a platform for exploring unconventional superconductivity beyond cuprates and pnictides.

cond-mat.supr-con↗

arXiv2026

MV-SAM3D: Adaptive Multi-View Fusion for Layout-Aware 3D Generation

Recent unified 3D generation models have made remarkable progress in producing high-quality 3D assets from a single image. Notably, layout-aware approaches such as SAM3D can reconstruct multiple objects while preserving their spatial arrangement, opening the door to practical scene-level 3D generation. However, current methods are limited to single-view input and cannot leverage complementary multi-view observations, while independently estimated object poses often lead to physically implausible layouts such as interpenetration and floating artifacts. We present MV-SAM3D, a training-free framework that extends layout-aware 3D generation with multi-view consistency and physical plausibility. We formulate multi-view fusion as a Multi-Diffusion process in 3D latent space and propose two adaptive weighting strategies -- attention-entropy weighting and visibility weighting -- that enable confidence-aware fusion, ensuring each viewpoint contributes according to its local observation reliability. For multi-object composition, we introduce physics-aware optimization that injects collision and contact constraints both during and after generation, yielding physically plausible object arrangements. Experiments on standard benchmarks and real-world multi-object scenes demonstrate significant improvements in reconstruction fidelity and layout plausibility, all without any additional training. Code is available at https://github.com/devinli123/MV-SAM3D.

cs.CV↗

arXiv2026

Energization of Proton via Beam-Driven Ion Bernstein Waves in p11B Plasmas

Energizing background ions plays a pivotal role in all forms of thermal nuclear fusion, as it can increase the fusion reaction rate without affecting the overall mechanical equilibrium. This is particularly critical for p11B fusion due to its exceptionally high operating temperature and substantial energy losses from bremsstrahlung radiation. Here, we report a nonlinear mechanism that efficiently transfers the energy of injected heating beams to background protons in p11B mixed plasmas, via fully kinetic Particle-In-Cell (PIC) simulations. When a proton neutral beam is injected into p11B plasmas, it triggers the excitation of ion Bernstein waves (IBWs) at harmonics of the proton cyclotron frequency. In the initial linear stage, the energy channels to background electrons and protons might be comparable, consistent with theoretical model for the energy transfer. However, in the latter nonlinear stage, the dominant channel transfers to background protons, generating a non-Maxwellian population of energetic protons. This transition is driven by a nonlinear spectral cascade of IBWs toward lower frequencies and longer wavelengths, which strengthens wave proton coupling while suppressing wave electron coupling.

physics.plasm-ph↗

arXiv2026

A unified SPH framework for shell-related interactions

A unified Smoothed Particle Hydrodynamics (SPH) framework is proposed to simulate interaction dynamics involving thin shells modeled by a reduced-dimensional, single-layer particle discretization, as opposed to full-dimensional SPH solids. The framework encompasses one-sided fluid-shell interactions, with the fluid present on only one side of the shell, as well as solid-shell, shell-shell, and shell-self interactions The study introduces a novel concept of imaginary shell contact particles, generated by projecting real shell particles along the local normal direction within the cut-off radius of the fluid particle, thereby mapping this reduced-dimensional shell model into a full-dimensional representation. With the volume of the imaginary particles defined based on the local shell curvature, the projection preserves kernel completeness for fluid-shell interactions while leaving the fluid-structure interaction (FSI) dynamics unchanged, such that the fluid-shell coupling algorithm is the same as in standard fluid-solid coupling. In addition, a particle-to-particle contact model for solid-solid interactions is developed by analogy to fluid dynamics: a contact density is computed using a fluid-style density initialization, and the resulting contact forces follow a momentum-equation-inspired formulation. Combined with the projection strategy, this contact formulation is directly extended to efficiently handle shell-related contact problems. The proposed method is validated using a series of benchmark tests, demonstrating stable and accurate performance across diverse interaction scenarios.

physics.flu-dyn↗

arXiv2025

A GPU-Accelerated Fully Coupled Fluid-Solid-Thermal SPH Solver for Industrial Gearboxes: Application to Lubricant Flow and Heat Transfer in a Bevel-Helical Reducer

This study presents a GPU-accelerated, fully coupled fluid-solid-thermal Smoothed Particle Hydrodynamics (SPH) framework for high-fidelity analysis of splash-lubricated gearboxes. A series of thermo-fluid simulations of a bevel-helical gear reducer were conducted by varying shaft speed, oil immersion depth, and lubricant viscosity to evaluate their influence on splash dynamics, churning losses, and lubricant temperature rise. The results show that churning losses increase by nearly an order of magnitude as the speed rises from 150 to 600 rad/s, while the corresponding lubricant temperature rise becomes approximately three to four times smaller. Variations in immersion depth and viscosity adjust the heating rate only modestly-typically within 10-20%-with their influence reversing between low- and high-speed regimes. The GPU backend provides a 7-9 speedup over a high-performance desktop CPU, enabling multi-million-particle, full-gearbox thermo-fluid simulations without specialized hardware. These findings demonstrate the feasibility of high-fidelity thermal analysis of industrial gearboxes and provide quantitative insight into the coupled splash, churning, and heat-transfer mechanisms that govern gearbox thermal performance.

physics.flu-dyn↗

arXiv2025

Patient-Scale Blood Flow Analysis in Artery Stent Implantation via Smoothed-Particle Hydrodynamics

A unified Smoothed Particle Hydrodynamics (SPH) simulation framework for coronary stent implantation is developed, which unifies weakly compressible hemodynamics, Neo-Hookean solids, and stent-artery contacts, based on a multi-resolution particle discretization. Prior to application, feasibility and accuracy are established via three baseline validations: (i) poiseuille flow in a two-dimensional channel with prescribed parabolic inflow and a pressure outlet, maintaining parabolic profiles with low Root Mean Squared Error of Prediction (RMSEP); (ii) channel flow initialized with a uniform velocity field and driven by a specified inlet-outlet pressure differential, with agreement to reference profiles quantified by low RMSEP at five reference instants; and (iii) a three-ring impact benchmark in solid mechanics, capturing large deformation, multi-body contact, and self-contact. The validated framework is subsequently applied to a coronary bifurcation with a focal stenosis, where flow-field diagnostics reveal acceleration at the stenotic throat, near-wall low-velocity zones, and co-localization of elevated pressure with increased Von Mises stress at the bifurcation and inlet. Following simulated stent implantation, velocity transitions across the stenosis become smoother, pressure gradients are reduced, and the fractional flow reserve increases from 0.45 to 0.91. These results demonstrate that the proposed SPH framework yields quantitatively reliable, clinically interpretable hemodynamic metrics alongside robust solid-solid contact predictions, thereby supporting rigorous analysis and pre-procedural planning of vascular interventions.

physics.flu-dyn↗

arXiv2025

Temporal filtered quantum sensing with the nitrogen-vacancy center in diamond

Nitrogen vacancy centers in diamond are among the leading solid state quantum platforms, offering exceptional spatial resolution and sensitivity for applications such as magnetic field sensing, thermometry, and bioimaging. However, in high background environments,such as those encountered in in vitro diagnostics, the performance of NV based sensors can be compromised by strong background fluorescence, particularly from substrates such as nitrocellulose. In this work, we analytically and experimentally investigate the use of pulsed laser excitation combined with time gating techniques to suppress background fluorescence and enhance the signal to noise ratio in NV based quantum sensing, with an emphasis on spin enhanced biosensing. Through experimental studies using mixed ensembles of silicon vacancy and NV centers in bulk diamond, as well as fluorescent nanodiamonds on NC substrates, we demonstrate significant improvements in NV spin resonance visibility, demonstrated by an increase of the SNR by up to 4x, and a resulting measurement time reduction by 16x. The presented technique and results here can help significantly increase the readout efficiency and speed in future applications of NV centers in high background environments, such as in IVD, where the NV centers are used as a fluorescent label for biomolecules.

quant-ph↗

arXiv2025

Toward Efficient FSI Modeling in Patient-Specific Arteries: SPH Simulation of Blood Flow in Thin Deformable Vessels

Accurate simulation of blood flow in deformable vessels is critical in cardiovascular research for understanding disease progression and informing clinical decision-making. However, due to the thin-walled nature of arteries, traditional smoothed particle hydrodynamics (SPH) approaches based on full-dimensional volume modeling often require extremely fine particle spacing to ensure numerical convergence for the solid mechanics. This, in turn, leads to redundant resolution in the fluid domain to maintain sufficient kernel support near the fluid-solid interface in fluid-structure interaction (FSI) simulations. To address this limitation, we propose an efficient reduced-dimensional shell-based SPH method for modeling thin-walled deformable arteries, and conduct FSI for capturing hemodynamics and arterial wall mechanics. Through a series of validation cases, the proposed shell model demonstrates comparable accuracy in fluid dynamics to the volume model, while achieving faster convergence in solid mechanics and reduced computational cost. We further investigate the influence of wall compliance on flow transitions and key hemodynamic indices, highlighting the necessity of FSI modeling over rigid-wall assumptions. Finally, the method is applied to two patient-specific vascular geometries, i.e. the carotid artery and the aorta, which demonstrates its robustness, efficiency and physiological relevance in realistic cardiovascular simulations.

cs.CE↗

arXiv2025

Efficient Utility-Preserving Machine Unlearning with Implicit Gradient Surgery

Machine unlearning (MU) aims to efficiently remove sensitive or harmful memory from a pre-trained model. The key challenge is to balance the potential tradeoff between unlearning efficacy and utility preservation, which involves forgetting undesirable information as defined while maintaining the model's original performance. One potential way to tackle this problem is to use multi-objective optimization to jointly optimize both the unlearning and utility preservation objectives. However, existing multi-objective methods only guarantee finding a Pareto-optimal solution without fine-grained control, which causes under-optimization of the unlearning objective. To this end, we first model MU as a constrained optimization problem, that is, optimizing the unlearning objective under the constraint of a bounded increase for utility loss. We then show that solving this optimization problem is equivalent to unilateral gradient surgery on the unlearning objective. To resolve the additional computational cost brought by gradient surgery, we propose an implicit gradient surgery method, which approximates the solution to the aforementioned constrained optimization problem via only one backpropagation, thereby achieving efficient utility-preserving MU. Theoretically, we provide a tight convergence analysis of the algorithm. Empirically, our extensive experiments show that the proposed algorithm achieves better tradeoff results than existing baselines. Codes are available at https://github.com/anseryuer/EUPMU-Efficient-Utility-Preserving-Machine-Unlearning.

cs.LG↗

arXiv2025

Anomalous terahertz nonlinearity in disordered s-wave superconductor close to the superconductor-insulator transition

Detection of the Higgs mode in superconductors using nonlinear terahertz spectroscopy is a key area of interest in condensed matter physics. We investigate the influence of disorder on the nonlinear terahertz response and the Higgs mode in NbN thin films with varying Ioffe-Regel parameters ($k_Fl$). In strongly disordered films near the superconductor-insulator transition (SIT), we observe an anomalous third-harmonic generation (THG) signal above $T_c$, which is absent in both cleaner superconducting and non-superconducting counterparts. The persistence of this normal-state THG signal in a high magnetic field excludes superconducting fluctuations as its origin. Below $T_c$, the THG intensity increases sharply, indicating a dominant contribution from the driven Higgs mode. The THG spectrum of the strongly disordered sample exhibits a broadened, multi-peak structure, which we attribute to quantum path interference between distinct channels involving unpaired electrons and Cooper pairs within emergent superconducting islands. Our findings not only demonstrate how disorder tunes the nonlinear terahertz response but also uncover a strong coupling between electrons responsible for normal-state THG and the superconducting Higgs mode below $T_c$ in strongly disordered samples.

cond-mat.supr-con↗

arXiv2025

Proactive Scene Decomposition and Reconstruction

Human behaviors are the major causes of scene dynamics and inherently contain rich cues regarding the dynamics. This paper formalizes a new task of proactive scene decomposition and reconstruction, an online approach that leverages human-object interactions to iteratively disassemble and reconstruct the environment. By observing these intentional interactions, we can dynamically refine the decomposition and reconstruction process, addressing inherent ambiguities in static object-level reconstruction. The proposed system effectively integrates multiple tasks in dynamic environments such as accurate camera and object pose estimation, instance decomposition, and online map updating, capitalizing on cues from human-object interactions in egocentric live streams for a flexible, progressive alternative to conventional object-level reconstruction methods. Aided by the Gaussian splatting technique, accurate and consistent dynamic scene modeling is achieved with photorealistic and efficient rendering. The efficacy is validated in multiple real-world scenarios with promising advantages.

cs.CV↗