arXiv subjects

Ying Dai

Publications and source records attributed to Ying Dai.

At least 37 records · Page 2Linked to original sources

arXiv2024

Gate-Controllable Quadri-Layertronics in 2D Multiferroic Antiferromagnet

Layertronics that manifests layer Hall effect is typically considered to intrinsically possess binary physics. Using symmetry arguments and a low-energy kp model, we show that the layer physics in layertronics can be engineered into quaternary mode, giving rise to the concept of quadri-layertronics. The mechanism correlates to the interplay between out-of-plane ferroelectricity and valley physics in antiferromagnetic multiferroic quadrilayer, which enables the layer-locked Berry curvature and Hall effect, i.e., deflecting the carriers with four different layer physics to move in specific directions. More importantly, the quadri-layertronics can be generated and manipulated by controlling the interlayer dipole arrangements via a gate voltage, allowing for the selective induction and detection of layer Hall effect in specific layers. Using first principles calculations, we further demonstrate the gate control of quadri-layertronics in multiferroic antiferromagnet of quadrilayer OsCl2. These explored phenomena and insights greatly enrich the research on layertronics.

cond-mat.mtrl-sci↗

arXiv2024

Exploring PCA-based feature representations of image pixels via CNN to enhance food image segmentation

For open vocabulary recognition of ingredients in food images, segmenting the ingredients is a crucial step. This paper proposes a novel approach that explores PCA-based feature representations of image pixels using a convolutional neural network (CNN) to enhance segmentation. An internal clustering metric based on the silhouette score is defined to evaluate the clustering quality of various pixel-level feature representations generated by different feature maps derived from various CNN backbones. Using this metric, the paper explores optimal feature representation selection and suitable clustering methods for ingredient segmentation. Additionally, it is found that principal component (PC) maps derived from concatenations of backbone feature maps improve the clustering quality of pixel-level feature representations, resulting in stable segmentation outcomes. Notably, the number of selected eigenvalues can be used as the number of clusters to achieve good segmentation results. The proposed method performs well on the ingredient-labeled dataset FoodSeg103, achieving a mean Intersection over Union (mIoU) score of 0.5423. Importantly, the proposed method is unsupervised, and pixel-level feature representations from backbones are not fine-tuned on specific datasets. This demonstrates the flexibility, generalizability, and interpretability of the proposed method, while reducing the need for extensive labeled datasets.

cs.CV↗

arXiv2024

Ferro-Valleytricity with In-Plane Magnetization

Ferro-valleytricity, a fundamental phenomenon that manifests spontaneous valley polarization, is generally considered to occur in two-dimensional (2D) materials with out-of-plane magnetization. Here, we propose a mechanism to realize ferro-valleytricity in 2D materials with in-plane magnetization, wherein the physics correlates to non-collinear magnetism in triangular lattice. Our model analysis provides comprehensive ingredients that allows for in-plane ferro-valleytricity, revealing that mirror symmetry is required for remarkable valley polarization and time-reversal-mirror joint-symmetry should be excluded. Through modulating in-plane magnetization offset, the valley polarization could be reversed. Followed by first-principles, such mechanism is demonstrated in a multiferroic triangular lattice of single-layer W3Cl8. We further show that the reversal of valley polarization could also be driven by applying electric field that modulates ferroelectricity. Our findings greatly enrich the valley physics research and significantly extend the scope for material classes of ferro-valleytricity.

cond-mat.mtrl-sci↗

arXiv2024

Small exciton effective mass in QL Bi2Se2Te: A material platform towards high-temperature excitonic condensate

Using first-principles simulations combined with many-body calculations, we show that two-dimensional free-standing quintuple-layer Bi2Se2Te is an inversion symmetric monolayer expected to achieve spatially indirect exciton with large exciton radius, small exciton effective mass and long exciton lifetime. Such system is theoretically predicted to be a promising platform for realizing excitonic Bose-Einstein condensation and superfluid due to its high phase transition temperatures of ~257 K and ~64.25 K for the BEC and excitonic superfluid, respectively. The importance of spin-orbit coupling is revealed, and the angular momentum selection rules for photon absorption are discussed. This finding suggests the potential of QL Bi2Se2Te monolayer with exotic bosonic bound states provides as a tantalizing high-temperature platform to probe excitonic physics.

cond-mat.mtrl-sci↗

arXiv2024

Coupling multi-space topologies in 2D ferromagnetic lattice

Topology can manifest topological magnetism (e.g., skyrmion and bimeron) in real space and quantum anomalous Hall (QAH) state in momentum space, which have changed the modern conceptions of matter phase. While the topologies in different spaces are widely studied separately, their coexistence and coupling in single phase is seldomly explored. Here, we report a novel phenomenon that arises from the interaction of topological magnetism and band topology, the multi-space topology, in 2D ferromagnetic lattice. Based on continuum theory and tight-binding model, we reveal that the interconnection between skyrmion/bimeron and QAH state generates distinctive localized chiral bound states (CBSs). With moderating topological magnetism through magnetic field, the multi-space topologies accompanied with different CBSs can be reversed, facilitating the coupling of multi-space topologies. By performing firstprinciples and atomic spin model simulations, we further demonstrate such multi-space topologies and their coupling in monolayer Cr2NSb. These results represent an important step towards the development of multispace topological phenomena in 2D lattice.

cond-mat.mtrl-sci↗

arXiv2024

Ferroelectrovalley in Two-Dimensional Multiferroic Lattices

Engineering valley index is essential and highly sought for valley physics, but currently it is exclusively based on the paradigm of the challenging ferrovalley with spin-orientation reversal under magnetic field. Here, an alternative strategy, i.e., the so-called ferroelectrovalley, is proposed to tackle the insurmountable spin-orientation reversal, which reveres valley index with the feasible ferroelectricity. Using symmetry arguments and tight-binding model, the C_2 rotation is unveiled to be able to take the place of time reversal for operating valley index in two-dimensional multiferroic kagome lattices, which enables the ferroelectricity-engineered valley index, thereby generating the concept of ferroelectrovalley. Based on first-principles calculations, this concept is further demonstrated in the breathing kagome lattice of single-layer Ti3Br8, wherein ferroelectricity couples the breathing process. These findings open a new direction for valleytronics and two-dimensional materials research.

cond-mat.mtrl-sci↗

arXiv2024

Topology-engineered orbital Hall effect in two-dimensional ferromagnets

Recent advances in manipulation of orbital angular momentum (OAM) within the paradigm of orbitronics present a promising avenue for the design of future electronic devices. In this context, the recently observed orbital Hall effect (OHE) occupies a special place. Here, focusing on both the second-order topological and quantum anomalous Hall insulators in two-dimensional ferromagnets, we demonstrate that topological phase transitions present an efficient and straightforward way to engineer the OHE, where the OAM distribution can be controlled by the nature of the band inversion. Using first-principles calculations, we identify Janus RuBrCl and three septuple layers of MnBi$_2$Te$_4$ as experimentally feasible examples of the proposed mechanism of OHE engineering by topology. With our work we open up new possibilities for innovative applications in topological spintronics and orbitronics.

cond-mat.mtrl-sci↗

arXiv2024

Recognizing Multiple Ingredients in Food Images Using a Single-Ingredient Classification Model

Recognizing food images presents unique challenges due to the variable spatial layout and shape changes of ingredients with different cooking and cutting methods. This study introduces an advanced approach for recognizing ingredients segmented from food images. The method localizes the candidate regions of the ingredients using the locating and sliding window techniques. Then, these regions are assigned into ingredient classes using a CNN (Convolutional Neural Network)-based single-ingredient classification model trained on a dataset of single-ingredient images. To address the challenge of processing speed in multi-ingredient recognition, a novel model pruning method is proposed that enhances the efficiency of the classification model. Subsequently, the multi-ingredient identification is achieved through a decision-making scheme, incorporating two novel algorithms. The single-ingredient image dataset, designed in accordance with the book entitled "New Food Ingredients List FOODS 2021", encompasses 9982 images across 110 diverse categories, emphasizing variety in ingredient shapes. In addition, a multi-ingredient image dataset is developed to rigorously evaluate the performance of our approach. Experimental results validate the effectiveness of our method, particularly highlighting its improved capability in recognizing multiple ingredients. This marks a significant advancement in the field of food image analysis.

cs.CV↗

arXiv2023

Bloch-type magnetic skyrmions in two-dimensional lattice

Magnetic skyrmions in two-dimensional lattice are a prominent topic of condensed matter physics and material science. Current research efforts in this field are exclusively constrained to Neel-type and antiskyrmion, while Bloch-type magnetic skyrmions are rarely explored. Here, we report the discovery of Bloch-type magnetic skyrmions in two-dimensional lattice of MnInP2Te6, using firstprinciples calculations and Monte-Carlo simulations. Arising from the joint effect of broken inversion symmetry and strong spin-orbit coupling, monolayer MnInP2Te6 presents large Dzyaloshinskii-Moriya interaction. This, along with ferromagnetic exchange interaction and out-ofplane magnetic anisotropy, gives rise to skyrmion physics in monolayer MnInP2Te6, without needing magnetic field. Remarkably, different from all previous works on two-dimensional lattice,the resultant magnetic skyrmions feature Bloch-type, which is protected by D3 symmetry.Furthermore, the Bloch-type magnetic bimerons are also identified in monolayer MnTlP2Te6. The phase diagrams of these Bloch-type topological magnetisms under magnetic field, temperature and strain are mapped out. Our results greatly enrich the research on magnetic skyrmions in twodimensional lattice.

cond-mat.mtrl-sci↗

arXiv2022

Ferroelectric higher-order topological insulator in two dimensions

The interplay between ferroelectricity and band topology can give rise to a wide range of both fundamental and applied research. Here, we map out the emergence of nontrivial corner states in two-dimensional ferroelectrics, and remarkably demonstrate that ferroelectricity and corner states are coupled together by crystallographic symmetry to realize the electric control of higher-order topology. Implemented by density functional theory, we identify a series of experimentally synthesized two-dimensional ferroelectrics, such as In$_2$Se$_3$, BN bilayers, and SnS, as realistic material candidates for the proposed ferroelectric higher-order topological insulators. Our work not only sheds new light on traditional ferroelectric materials but also opens an avenue to bridge the higher-order topology and ferroelectricity that provides a nonvolatile handle to manipulate the topology in next-generation electronic devices.

cond-mat.mtrl-sci↗

arXiv2022

Multiple Topological Magnetism in van der Waals Heterostructure of MnTe2/ZrS2

Topological magnetism in low-dimensional systems is of fundamental and practical importance in condensed-matter physics and material science. Here, using first-principles and Monte-Carlo simulations, we present that multiple topological magnetism (i.e., skyrmion and bimeron) can survive in van der Waals Heterostructure of MnTe2ZrS2. Arising from interlayer coupling, MnTe2ZrS2 can harbor a large Dzyaloshinskii-Moriya interaction. This, combined with ferromagnetic exchange interaction, yields an intriguing skyrmion phase consisting of sub-10 nm magnetic skyrmions under a tiny magnetic field of 75 mT. Meanwhile, upon harnessing a small electric field, magnetic bimeron can be observed in MnTe2ZrS2 as well, suggesting the existence of multiple topological magnetism. Through interlayer sliding, both topological spin textures can be switched on-off, suggesting their stacking-dependent character. In addition, the impacts of d and Keff on these spin textures are revealed, and a dimensionless parameter is utilized to describe their joint effect. These explored phenomena and insights not only are useful for fundamental research in topological magnetism, but also enable novel applications in nanodevices.

cond-mat.mtrl-sci↗

arXiv2022

Exploring CNN-based models for image's aesthetic score prediction with using ensemble

In this paper, we proposed a framework of constructing two types of the automatic image aesthetics assessment models with different CNN architectures and improving the performance of the image's aesthetic score prediction by the ensemble. Moreover, the attention regions of the models to the images are extracted to analyze the consistency with the subjects in the images. The experimental results verify that the proposed method is effective for improving the AS prediction. Moreover, it is found that the AS classification models trained on XiheAA dataset seem to learn the latent photography principles, although it can't be said that they learn the aesthetic sense.

cs.CV↗

arXiv2022

Orbital shift-induced boundary obstructed topological materials with a large energy gap

We propose boundary obstructed topological phases caused by Wannier orbital shift between ordinary atomic sites, which, however, cannot be indicated by symmetry eigenvalues at high symmetry momenta (symmetry indicators) in bulk. On the open boundary, Wannier charge centers can shift to different atoms from those in bulk, leading to in-gap surface states, higher-order hinge states or corner states. To demonstrate such orbital-shift-induced boundary obstructed topological insulators, we predict eight material candidates, all of which were overlooked in present topological databases. Metallic surface states, hinge states, or corner states cover the large bulk energy gap (for example, more than 1 eV in TlGaTe$_2$) at related boundary, which are ready for experimental detection. Additionally, we find these materials are also fragile topological insulators with hourglass like surface states.

cond-mat.mes-hall↗

arXiv2022

Intrinsic Layer-Polarized Anomalous Hall Effect in Bilayer MnBi2Te4

Layer-polarized anomalous Hall effect (LP-AHE) is an attractive phenomenon in condensed-matter physics from the standpoints of both fundamental interest and device applications. The current LP-AHE research is based on the extrinsic paradigm of using external electric fields, in which the generation and control of LP-AHE are not straightforward. Here, we propose a novel mechanism that realizes intrinsic LP-AHE in bilayer lattices, through the mediation of sliding physics and Berry curvature. Moreover, this mechanism could render the LP-AHE in a controllable and reversable fashion. We analyze the symmetry requirements for a system to host such intrinsic LP-AHE. Its validity is further demonstrated in a real material of bilayer MnBi2Te4. By stacking with broken inversion symmetry, the layer-locked Berry curvature enables the intrinsic LP-AHE in bilayer MnBi2Te4, and the switchable control of its LP-AHE is achieved by sliding ferroelectricity. Our work opens a significant new direction for LP-AHE and two-dimensional (2D) materials research.

cond-mat.mtrl-sci↗

arXiv2022

Layer-Polarized Anomalous Hall Effect in Valleytronic van der Waals Bilayers

Layer-polarized anomalous Hall effect (LP-AHE), derived from the coupling between Berry curvature and layer degree of freedom, is of importance for both fundamental physics and device applications. Nonetheless, the current research paradigm is rooted in topological systems, rendering such phenomenon rather scarce. Here, through model analysis, we propose an alternative, but general mechanism to realize the LP-AHE in valleytronic van der Waals bilayers by interlayer sliding. The interaction between the out-of-plane ferroelectricity and A-type antiferromagnetism gives rise to the layer-locked Berry curvature and thus the long-sought LP-AHE in the bilayer systems. The LP-AHE can be strongly coupled with sliding ferroelectricity, to enable ferroelectrically controllable and reversible. The mechanism is demonstrated in a series of real valleytronic materials, including bilayer VSi2P4, VSi2N4, FeCl2, RuBr2 and VClBr. The new mechanism and phenomena provide a significant new direction to realize LP-AHE and explore its application in electronics.

cond-mat.mtrl-sci↗

arXiv2022

Antiferromagnetic skyrmion crystal in Janus monolayer CrSi2N2As2

Antiferromagnetic skyrmion crystal (AF-SkX), a regular array of antiferromagnetic skyrmions, is a fundamental phenomenon in the field of condensed-matter physics. So far, only very few proposals have been made to realize the AF-SkX, and most based on three-dimensional (3D) materials. Herein, using first-principles calculations and Monte-Carlo simulations, we report the identification of AF-SkX in two-dimensional lattice of Janus monolayer CrSi2N2As2. Arising from the broken inversion symmetry and strong spin-orbit coupling, large Dzyaloshinskii-Moriya interaction is obtained in Janus monolayer CrSi2N2As2. This, combined with the geometric frustration of its triangular lattice, gives rise to the skyrmion physics and long-sought AF-SkX in the presence of external magnetic field. More intriguingly, this system presents two different antiferromagnetic skyrmion phases, and such phenomenon is distinct from those reported in 3D systems. Furthermore, by contacting with Sc2CO2, the creation and annihilation of AF-SkX in Janus monolayer CrSi2N2As2 can be achieved through ferroelectricity. These findings greatly enrich the research on antiferromagnetic skyrmions.

cond-mat.mtrl-sci↗

arXiv2022

2D magnetoelectric multiferroics in MnSTe/In2Se3 heterobilayer with ferroelectrically controllable skyrmions

The magnetoelectric effect and skyrmions are two fundamental phenomena in the field of condensed-matter physics. Here, using first-principles calculations and Monte-Carlo simulations, we propose that strong magnetoelectric coupling can be demonstrated in a multiferroic heterobilayer consisting of two-dimensional (2D) MnSTe and α-In2Se3. As the electric polarization in ferroelectric α-In2Se3 is switched, the creation and annihilation of topological magnetic phase can be achieved in this multiferroic heterobilayer, giving rise to the intriguing ferroelectrically controllable skyrmions. This feature is further revealed to be closely related to the physical quantity of D2/|KJ|, which is generally applicable for describing the required conditions of such physics. Moreover, the evaluations of their topological magnetic phases with temperature are systematically discussed. These insights not only greatly enrich the research on 2D magnetoelectric multiferroics, but also pave a promising avenue to realize new skyrmionic device concepts.

cond-mat.mtrl-sci↗

arXiv2022

Spontaneous magnetic skyrmions in single-layer CrInX3(X=Te, Se)

The realization of magnetic skyrmions in nanostructures holds great promise for both fundamental research and device applications. Despite recent progress, intrinsic magnetic skyrmions in two-dimensional lattice are still rarely explored. Here, using first-principles calculations and Monte-Carlo simulations, we report the identification of spontaneous magnetic skyrmions in single-layer CrInX3 (X = Te, Se). Due to the joint effect of broken inversion symmetry and strong spin-orbit coupling, inherent large Dzyaloshinskii-Moriya interaction occurs in both systems, endowing the intriguing Neel-type skyrmions in the absence of magnetic field. By further imposing moderate magnetic field, the skyrmion phase can be obtained and is stable within a wide temperature range. Particularly for single-layer CrInTe3, the size of skyrmions is sub-10 nm and the skyrmion phase can be maintained at an elevated temperature of 180 K. In addition, the phase diagrams of their topological spin textures under the variation of magnetic parameters of D, J, and K are mapped out. Our results greatly enrich the research of 2D skyrmionics physics.

cond-mat.mtrl-sci↗