Emergence of Stable Meron Quartets in Twisted Magnets

Kim, Kyoung-Min; Go, Gyungchoon; Park, Moon Jip; Kim, Se Kwon

doi:10.1021/acs.nanolett.3c03246

Cited by 4 publications

(11 citation statements)

References 48 publications

(124 reference statements)

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“…Similar ring-shaped bimeron patterns were recently addressed in [ 61 ] through atomistic spin simulations on a twisted bilayer magnet CrCl 3 . It was highlighted that 2D vdW magnets with an additional twist between layers open a unique avenue for investigating the properties of bimerons with remarkable flexibility, either through external stimuli or through the creation of heterostructures.…”

Section: Bimeron “Macromolecules”supporting

confidence: 74%

“Polymerization” of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy

Mukai,

Leonov

2024

Nanomaterials

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We re-examine the internal structure of bimerons, which are stabilized in easy-plane chiral magnets and represent coupled states of two merons with the same topological charge |1/2| but with opposite vorticity and the polarity. We find that, in addition to the vortices and antivortices, bimerons feature circular regions which are located behind the anti-vortices and bear the rotational sense opposite to the rotational sense chosen by the Dzyaloshinskii–Moriya interaction. In an attempt to eliminate these wrong-twist regions with an excess of positive energy density, bimerons assemble into chains, and as such exhibit an attracting interaction potential. As an alternative to chains, we demonstrate the existence of ring-shaped bimeron clusters of several varieties. In some rings, bimeron dipoles are oriented along the circle and swirl clockwise and/or counterclockwise (dubbed “roundabouts”). Moreover, a central meron encircled by the outer bimerons may possess either positive or negative polarity. In other rings, the bimeron dipoles point towards the center of a ring and consequently couple to the central meron (dubbed “crossings”). We point out that the ringlike solutions for baryons obtained within the Skyrme model of pions, although driven by the same tendency of the energy reduction, yield only one type of bimeron rings. The conditions of stability applied to the described bimeron rings are additionally extended to bimeron networks when bimerons fill the whole space of two-dimensional samples and exhibit combinations of rings and chains dispersed with different spatial density (dubbed bimeron “polymers”). In particular, bimeron crystals with hexagonal and the square bimeron orderings are possible when the sides of the unit cells represent chains of bimerons joined in intersections with three or four bimerons, respectively; otherwise, bimeron networks represent disordered bimeron structures. Moreover, we scrutinize the inter-transformations between hexagonal Skyrmion lattices and disordered bimeron polymers occuring via nucleation and mutual annihilation of merons within the cell boundaries. Our theory provides clear directions for experimental studies of bimeron orderings in different condensed-matter systems with quasi-two-dimensional geometries.

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Section: Bimeron “Macromolecules”supporting

confidence: 74%

“Polymerization” of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy

Mukai,

Leonov

2024

Nanomaterials

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“…Both NCD and MD phases exhibit moiré periodicity, leading to the periodic domain patterns (Fig. 2(d-e)), which we refer to as "nanoscale magnetic domain arrays" [20].…”

Section: A Dataset Generationmentioning

confidence: 99%

“…11. We computed the magnetic ground state for each parameter set by employing 50 different random initial spin configurations and relaxing each configuration using an iterative optimization method [20]. During the relaxation, periodic boundary conditions were imposed on the boundary of the moiré supercell.…”

Section: Appendix A: Dataset Preparationmentioning

confidence: 99%

“…1(a), accurately estimates the parameters of the magnetic Hamiltonian from magnetic domain images generated through atomistic spin simulations. This model resolves an inverse problem associated with inferring the parameters from the observed data, a feat beyond the reach of established theoretical methods [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Our generative model, depicted in Fig.…”

mentioning

confidence: 93%

“…1 predefined magnetic parameters. This model efficiently handles the complexity of the magnetic Hamiltonian without compromising accuracy, thereby mitigating the need for resource-intensive atomistic spin simulations [8][9][10][19][20][21]. These advancements not only extend the applicability of DNN techniques to twisted van der Waals magnets but also streamline future investigations into these captivating systems.…”

mentioning

confidence: 98%

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A Study on Educational Implications of ‘Allegory of Cave’ in Plato’s Republic

Lee¹

2023

Edu Res Institute Kongju National Univ

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The aim of this study is to analyze and translate ‘Allegory of Cave’ in Plato’s Republic, vol. 7 from an educational perspective, focusing on the unique meaning and importance of allegory. For achieving this aim, researcher firstly tried to reconstruct forms of this allegory, introduced by Plato in a conversational type step by step, and tried to identify many educational implications involved in this allegory in three main aspects. Conclusions are as follows; Firstly, researcher found that concept of ‘conversional education’ handled as important assignment of educational work in allegory. In view of this suggestion, educators would be rethinking critically and be prepared to change their traditional concept of education. Secondly, researcher found that removing prejudices or preconceptions is an important assignment for educational activities in this allegory. In view of this discovery, educators would make efforts to remove prejudices or preconceptions before teaching specific knowledge or information. Lastly, researcher discovered that one of the important attitudes of educators is to have the humanity toward ignorant and stupid people in the allegory. In this view, educators would provide their own true knowledge or information to the ignorant. In addition to this implications, researcher tried to suggest the possibilities of re-translating the ‘Allegory of Cave’ for having meaningful connotations and implications.

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Deep learning methods for Hamiltonian parameter estimation and magnetic domain image generation in twisted van der Waals magnets

Lee,

Song,

Kim

2024

Mach. Learn.: Sci. Technol.

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The application of twist engineering in van der Waals magnets has opened new frontiers in the field of two-dimensional magnetism, yielding distinctive magnetic domain structures. Despite the introduction of numerous theoretical methods, limitations persist in terms of accuracy or efficiency due to the complex nature of the magnetic Hamiltonians pertinent to these systems. In this study, we introduce a deep-learning approach to tackle these challenges. Utilizing customized, fully connected networks, we develop two deep-neural-network kernels that facilitate efficient and reliable analysis of twisted van der Waals magnets. Our regression model is adept at estimating the magnetic Hamiltonian parameters of twisted bilayer CrI3 from its magnetic domain images generated through atomistic spin simulations. The ‘generative model’ excels in producing precise magnetic domain images from the provided magnetic parameters. The trained networks for these models undergo thorough validation, including statistical error analysis and assessment of robustness against noisy injections. These advancements not only extend the applicability of deep-learning methods to twisted van der Waals magnets but also streamline future investigations into these captivating yet poorly understood systems.

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Emergence of Stable Meron Quartets in Twisted Magnets

Cited by 4 publications

References 48 publications

“Polymerization” of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy

“Polymerization” of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy

A Study on Educational Implications of ‘Allegory of Cave’ in Plato’s Republic

Deep learning methods for Hamiltonian parameter estimation and magnetic domain image generation in twisted van der Waals magnets

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