arXiv subjects

Yuhui Huang

Publications and source records attributed to Yuhui Huang.

15 recordsLinked to original sources

arXiv2026

Optimal Local Error Estimates for Finite Element Methods with Measure-Valued Sources

We study finite element approximations of second-order elliptic problems with measure-valued right-hand sides supported on lower-dimensional sets. The exact solution generally lacks $H^1$-regularity due to the source singularity, which limits global convergence rates of numerical methods. Using a very weak solution framework, we establish well-posedness and global error estimates for standard Lagrange finite element methods on Lipschitz polyhedral/polygonal domains. By using interior estimates techniques, we prove optimal local $L^2$- and $H^1$-error estimates in subdomains that are strictly separated from the support of the measure. Extensive numerical experiments are provided to verify the theoretical results. These results show that for Lagrange FEMs solving elliptic problems with singular right-hand sides, the loss of global convergence is purely local, and that optimal convergence rates still hold away from the singular source.

math.NA↗

arXiv2026

Thermally Configurable Multi-Order Polar Skyrmions in Multiferroic Oxide Superlattices

Polar topological textures in low-dimensional ferroelectrics have emerged as a versatile platform for high-density information storage and neuromorphic computing. While low-order topological states, such as vortices and skyrmions, have been extensively studied, high-order polar topological families remain largely unexplored due to their higher energy requirements and limited stabilization methods. Here, using a BiFeO3 (BFO)-based multiferroic superlattice as a model system, we demonstrate a thermal-modulation strategy that stabilizes multi-order polar skyrmions and enables reversible tuning of their topological order through phase-field simulations. It was found that temperature modulation drives the system from polar solitons through 1{\pi}-, 2{\pi}-, 3{\pi}-, and 4{\pi}-skyrmion states, with closed heating-cooling path analyses revealing the widest thermal stability window for 2{\pi}-skyrmions (up to 600 K). Leveraging this robustness, 2% Sm doping in BFO lowers the transition temperatures, enabling room-temperature stabilization of 2{\pi}-skyrmions. These findings enrich the fundamental understanding of multi-order polar topologies and establish a tunable strategy for realizing variable-order topological configurations in practical memory devices.

cond-mat.mtrl-sci↗

arXiv2025

Analysis of A Mixed Finite Element Method for Poisson's Equation with Rough Boundary Data

This paper is concerned with finite element methods for Poisson's equation with rough boundary data. Conventional methods require that the boundary data $g$ of the problem belongs to $H^{1/2} (\partial \Omega)$. However, in many applications one has to consider the case when $g$ is in $L^2(\partial \Omega)$ only. To this end, very weak solutions are considered to establish the well-posedness of the problem. Most previously proposed numerical methods use regularizations of the boundary data. The main purpose of this paper is to use the Raviart--Thomas mixed finite element method to solve the Poisson equation with rough boundary data directly. We prove that the solution to the proposed mixed method converges to the very weak solution. In particular, we prove that the convergence rate of the numerical solution is $O(h^{1/2})$ in convex domains and $O(h^{s-1/2})$ in nonconvex domains, where $s > 1/2$ depends on the geometry of the domain. The analysis is based on a regularized approach and a rigorous estimate for the corresponding dual problem. Numerical experiments confirm the theoretically predicted convergence rates for the proposed mixed method for Poisson's equation with rough boundary data.

math.NA↗

arXiv2025

Self-Supervised Noise Adaptive MRI Denoising via Repetition to Repetition (Rep2Rep) Learning

Purpose: This work proposes a novel self-supervised noise-adaptive image denoising framework, called Repetition to Repetition (Rep2Rep) learning, for low-field (<1T) MRI applications. Methods: Rep2Rep learning extends the Noise2Noise framework by training a neural network on two repeated MRI acquisitions, using one repetition as input and another as target, without requiring ground-truth data. It incorporates noise-adaptive training, enabling denoising generalization across varying noise levels and flexible inference with any number of repetitions. Performance was evaluated on both synthetic noisy brain MRI and 0.55T prostate MRI data, and compared against supervised learning and Monte Carlo Stein's Unbiased Risk Estimator (MC-SURE). Results: Rep2Rep learning outperforms MC-SURE on both synthetic and 0.55T MRI datasets. On synthetic brain data, it achieved denoising quality comparable to supervised learning and surpassed MC-SURE, particularly in preserving structural details and reducing residual noise. On the 0.55T prostate MRI dataset, a reader study showed radiologists preferred Rep2Rep-denoised 2-average images over 8-average noisy images. Rep2Rep demonstrated robustness to noise-level discrepancies between training and inference, supporting its practical implementation. Conclusion: Rep2Rep learning offers an effective self-supervised denoising for low-field MRI by leveraging routinely acquired multi-repetition data. Its noise-adaptivity enables generalization to different SNR regimes without clean reference images. This makes Rep2Rep learning a promising tool for improving image quality and scan efficiency in low-field MRI.

eess.IV↗

arXiv2025

PTST: A polar topological structure toolkit and database

Ferroelectric oxide superlattices with complex topological structures such as vortices, skyrmions, and flux closure domains have garnered significant attention due to their fascinating properties and potential applications. However, progress in this field is often impeded by challenges such as limited data-sharing mechanisms, redundant data generation efforts, high barriers between simulations and experiments, and the underutilization of existing datasets. To address these challenges, we have created the Polar Topological Structure Toolbox and Database(PTST). This community driven repository compiles both standard datasets from high throughput phase field simulations and user submitted nonstandard datasets. The PTST utilizes a Global Local Transformer (GL Transformer) to classify polarization states by dividing each sample into spatial sub blocks and extracting hierarchical features, resulting in ten distinct topological categories. Through the PTST web interface, users can easily retrieve polarization data based on specific parameters or by matching experimental images. Additionally, a Binary Phase Diagram Generator allows users to create strain and electric field phase diagrams within seconds. By providing ready-to-use configurations and integrated machine-learning workflows, PTST significantly reduces computational load, streamlines reproducible research, and promotes deeper insights into ferroelectric topological transitions.

cond-mat.mtrl-sci↗

arXiv2024

Machine learning assisted screening of metal binary alloys for anode materials

In the dynamic and rapidly advancing battery field, alloy anode materials are a focal point due to their superior electrochemical performance. Traditional screening methods are inefficient and time-consuming. Our research introduces a machine learning-assisted strategy to expedite the discovery and optimization of these materials. We compiled a vast dataset from the MP and AFLOW databases, encompassing tens of thousands of alloy compositions and properties. Utilizing a CGCNN, we accurately predicted the potential and specific capacity of alloy anodes, validated against experimental data. This approach identified approximately 120 low potential and high specific capacity alloy anodes suitable for various battery systems including Li, Na, K, Zn, Mg, Ca, and Al-based. Our method not only streamlines the screening of battery anode materials but also propels the advancement of battery material research and innovation in energy storage technology.

cond-mat.mtrl-sci↗

arXiv2023

A molecular Ferroelectric thin film of imidazolium perchlorate on Silicon

Molecular ferroelectric materials have attracted widespread attention due to their abundant chemical diversity, structural tunability, low synthesis temperature, and high flexibility. Meanwhile, the integration of molecular ferroelectric materials and Si is still challenging, while the fundamental understanding of the ferroelectric switching process is still lacking. Herein, we have successfully synthesized the imidazole perchlorate (ImClO4) single crystals and a series of high-quality highly-oriented thin films on a Si substrate. A high inverse piezoelectric coefficient (55.7 pm/V) is demonstrated for the thin films. Two types of domain bands can be observed (in the size of a few microns): type-I band tilts ~60° with respect to the horizontal axis, while the type-II band is perpendicular to the horizontal axis. Most of the domain walls (DWs) are 180° DWs for the two bands, while some 109° DWs can also be observed. Interestingly, the DWs in type-I band are curved, charged domain walls; while the 180° DWs in type-II band are straight, noncharged domain walls. After applying +20 V for 5 s through a PFM tip, the 180° DWs in type-I band shrink first, then disconnect from the band boundary, forming a needle-like domain with a size of ~100 nm. The needle-like domain will extend toward the band boundary after an inverse bias is applied (-20 V), and expand along the band boundary after touching the boundary. Whereas for the type-II domain band, the 180° DWs are more mobile than the 109° domain walls, which displaces ~500 nm after applying +20 V. While such displacement is much shorter after the application of a negative bias for the same duration, starting from the positively poled sample. We hope to spur further interest in the on-chip design of the molecular ferroelectrics based electronic devices.

cond-mat.mtrl-sci↗

arXiv2023

Dynamic motion of polar skyrmions in oxide heterostructures

Polar skyrmions have been widely investigated in oxide heterostructure recently, due to their exotic properties and intriguing physical insights. Meanwhile, so far, the external field-driven motion of the polar skyrmion, akin to the magnetic counterpart, has yet to be discovered. Here, using phase-field simulations, we demonstrate the dynamic motion of the polar skyrmions with integrated external thermal, electrical, and mechanical stimuli. The external heating reduces the spontaneous polarization hence the skyrmion motion barrier, while the skyrmions shrink under the electric field, which could weaken the lattice pinning and interactions between the skyrmions. The mechanical force transforms the skyrmions into c-domain in the vicinity of the indenter center under the electric field, providing the space and driving force needed for the skyrmions to move. This study confirmed that the skyrmions are quasi-particles that can move collectively, while also providing concrete guidance for the further design of polar skyrmion-based electronic devices.

cond-mat.mtrl-sci↗

arXiv2022

Mechanical configurable nanopatterning of polar topological states and formation of post-skyrmion

The controllable phase transition and nanopatterning of topological states in a ferroelectric system under external stimuli are critical for realizing the potential applications in nanoelectronic devices such as logic, memory, race-track, etc. Herein, using the phase-field simulations, we demonstrate the mechanical manipulation of polar skyrmions in ferroelectric superlattices by applying external local compressive stress through an atomic force microscopy (AFM) tip. Different switching pathways are observed: under small to moderate force (<1 uN), the skyrmions coalesce to form a long stripe; while increasing the applied load (e.g., above 2 uN) leads to the suppression of spontaneous polarization, forming a new metastable topological structure, namely the post-skyrmion. It is constructed by attaching multiple merons onto a center Bloch skyrmion, showing a topological charge of 1.5 (under 2 uN) or 2 (under 3 uN). We have further designed a mechanical nanopatterning process, where the stripes can form a designed pattern by moving the AFM tip (write), which can also be switched back to a full skyrmion state under an applied electric field (erase). We believe this study will spur further interest in mechanical manipulation and nanopatterning of polar topological phases through mechanical forces.

cond-mat.mtrl-sci↗

arXiv2022

Dynamics of the lithium metal electrodeposition: Effects of a gas bubble

Rechargeable lithium metal batteries have been widely investigated recently, driven by the global trend for the electrification of transportation. Understanding the dynamics of lithium metal electrodeposition is crucial to design safe and reliable lithium metal anodes. In this study, we developed a grand potential-based phase-field model to investigate the effect of a static gas bubble, which forms due to the complicated internal side reactions, on the dynamics of the dendrite growth during electrodeposition. It is observed that with the presence of a gas bubble, the dendrite growth is largely accelerated, due to the accumulation of lithium ions on the far side of the bubble away from the anode surface, which could serve as an ion "reservoir" for the dendrite growth, leading to the bending/tilting of the lithium dendrites toward the bubble. Meanwhile, the effects of the bubble size and distance to the anode are further studied, demonstrating that the larger the bubble size and the closer to the anode, the longer the lithium dendrites grow. We hope this study could serve as an example to exploit the effect of extrinsic factors on the dendrite growth dynamics.

cond-mat.mtrl-sci↗

arXiv2022

Surface engineering for ultrathin metal anodes enabling high-performance Zn-ion batteries

Zn metal battery has been considered a promising alternative energy storage technology in renewable energy storage and grid storage. It is well-known that the surface orientation of a Zn metal anode is vital to the reversibility of a Zn metal battery. Herein, the (101)-oriented thin Zn metal anode (down to 2 μm) is electrodeposited on a Cu surface by adding dimethyl sulfoxide (DMSO) electrolyte additive in ZnSO4 aqueous solution. Scanning electron microscope (SEM) observation indicates the formation of flat terrace-like compact (101)-oriented surfaces. Insitu optical observation confirms that the (101)-oriented surfaces can be reversibly plated and stripped. DFT calculations reveal two mechanisms for the nucleation and growth of the Zn-(101) surface: (1) formation of Zn(101)//Cu(001) could lower the interface energy as compared to Zn(002)//Cu(001); (2) large reconstruction of the Zn (101) surface with DMSO and H2O absorption. Raman, XPS, and ToF-SIMS characterizations indicate that adding DMSO in ZnCl2 could facilitate the formation of ZnO-based SEI on Zn metal surface, while OH- and S-based SEI can be obtained with DMSO in ZnSO4. The electrochemical testings are performed, which demonstrates a higher cyclability for the (101)-oriented Zn in the half cell as well as a lower charge transfer barrier with respect to the (002)-dominated surface of the same electrode thickness. Zn||V2O5 full cells are further assembled, showing better capacity retention for the (101)-Zn as compared to the (002)-Zn with the same thickness (5 μm, 3 μm, and 2 μm). We hope this study to spur further interest in the control of Zn metal surface crystallographic orientation towards ultrathin Zn metal anodes.

cond-mat.mtrl-sci↗

arXiv2021

Order-disorder transitions in a polar vortex lattice

Order-disorder transitions are widely explored in various vortex structures in condensed matter physics, i.e., in the type-II superconductors and Bose-Einstein condensates. In this study, we have investigated the ordering of the polar vortex phase in the (PZT)n/(STO)n superlattice systems through phase-field simulations. An antiorder state is discovered for short periodicity superlattice on an SSO substrate, owing to the huge interfacial coupling between PZT and STO as well as the giant in-plane polarization in STO layers due to the large tensile strain. Increasing the periodicity leads to the anti-order to disorder transition, resulting from the loss of interfacial coupling and disappearance of the polarization in STO layers. On the other hand, for short periodicity superlattices, order-disorder-antiorder transition can be engineered by mediating the substrate strain, due to the delicate competition between the depoling effect, interfacial coupling, and strain effect. We envision this study to spur further interest towards the understanding of order-disorder transition in ferroelectric topological structures.

cond-mat.mtrl-sci↗

arXiv2021

A Semantic Indexing Structure for Image Retrieval

In large-scale image retrieval, many indexing methods have been proposed to narrow down the searching scope of retrieval. The features extracted from images usually are of high dimensions or unfixed sizes due to the existence of key points. Most of existing index structures suffer from the dimension curse, the unfixed feature size and/or the loss of semantic similarity. In this paper a new classification-based indexing structure, called Semantic Indexing Structure (SIS), is proposed, in which we utilize the semantic categories rather than clustering centers to create database partitions, such that the proposed index SIS can be combined with feature extractors without the restriction of dimensions. Besides, it is observed that the size of each semantic partition is positively correlated with the semantic distribution of database. Along this way, we found that when the partition number is normalized to five, the proposed algorithm performed very well in all the tests. Compared with state-of-the-art models, SIS achieves outstanding performance.

cs.CV↗

arXiv2021

Local Manipulation of Polar Skyrmions and Topological Phase Transitions

Topological phases such as polar skyrmions have been a fertile playground for ferroelectric oxide superlattices, with exotic physical phenomena such as negative capacitance. Herein, using phase-field simulations, we demonstrate the local control of the skyrmion phase with electric potential applied through a top electrode. Under a relatively small electric potential, the skyrmions underneath the electrode can be erased and recovered reversibly. A topologically protected transition from the symmetric to asymmetric skyrmion bubbles is observed at the edge of the electrode. While a topological transition to a labyrinthine domain requires a high applied potential, it can switch back to the skyrmion state with a relatively small electric potential. The topological transition from +1 to 0 occurs before the full destruction of the bubble state. It is shown that the shrinking and bursting of the skyrmions leads to a large reduction in the dielectric permittivity, the magnitude of which depends on the size of the electrode.

cond-mat.mtrl-sci↗

arXiv2021

Machine Learning Enabled Prediction of Cathode Materials for Zn ion Batteries

Rechargeable Zn batteries with aqueous electrolytes have been considered as promising alternative energy storage technology, with various advantages such as low cost, high volumetric capacity, environmentally friendly, and high safety. However, a lack of reliable cathode materials has largely pledged their applications. Herein, we developed a machine learning (ML) based approach to predict cathodes with high capacity (>150 mAh/g) and high voltage (>0.5V). We screened over ~130,000 inorganic materials from the Materials Project database and applied the crystal graph convolutional neural network (CGCNN) based ML approach with data from the AFLOW database. The combination of these two could not only screen cathode materials that match well with the experimental data but also predict new promising candidates for further experimental validations. We hope this study could spur further interests in ML-based advanced theoretical tools for battery materials discovery.

cond-mat.mtrl-sci↗