This book summarizes some of the most exciting theoretical developments in the topological phenomena of skyrmions in noncentrosymmetric magnetic systems over recent decades. After presenting pedagogical backgrounds to the Berry phase and homotopy theory, the author systematically discusses skyrmions in the order of their development, from the Ginzburg-Landau theory, CP1 theory, Landau-Lifshitz-Gilbert theory, and Monte Carlo numerical approaches. Modern topics, such as the skyrmion-electron interaction, skyrmion-magnon interaction, and various generation mechanisms of the skyrmion are examined with a focus on their general theoretical aspects. The book concludes with a chapter on the skyrmion phenomena in the cold atom context. The topics are presented at a level accessible to beginning graduate students without a substantial background in field theory. The book can also be used as a text for those who wish to engage in the physics of skyrmions in magnetic systems, or as an introduction to the various theoretical methods used in studying current condensed-matter systems.

"The book reviews all the aspects of recent developments in research on skyrmions, from the presentation of the observation and characterization techniques to the description of physical properties and expected applications. It will be of great use for all scientists working in this field." – Albert Fert, 2007 Nobel Laureate in Physics (from the Foreword) A skyrmion is a tiny region of reversed magnetization – quasiparticles since they are not present except in a magnetic state, and also give rise to physics that cannot be described by Maxwell’s equations. These particles are fascinating subjects for theoretical and experimental studies. Moreover, as a new type of magnetic domain structure with special topological structures, skyrmions feature outstanding magnetic and transport properties and may well have applications in data storage and other advanced spintronic devices, as readers will see in this book. Chapters address the relationships between physical properties of condensed matter, such as the AB effect, Berry phase effect, quantum Hall effect, and topological insulators. Overall, it provides a timely introduction to the fundamental aspects and possible applications of magnetic skyrmions to an interdisciplinary audience from condensed matter physics, chemistry, and materials science.

Magnetic skyrmions are particle-like objects described by localized solutions of non-linear partial differential equations. Up until a few decades ago, it was believed that magnetic skyrmions only existed in condensed matter as short-term excitations that would quickly collapse into linear singularities. The contrary was proven theoretically in 1989 and evidentially in 2009. It is now known that skyrmions can exist as long-living metastable configurations in low-symmetry condensed matter systems with broken mirror symmetry, increasing the potential applications possible. Magnetic Skyrmions and their Applications delves into the fundamental principles and most recent research and developments surrounding these unique magnetic particles. Despite achievements in the synthesis of systems stabilizing chiral magnetic skyrmions and the variety of experimental investigations and numerical calculations, there have not been many summaries of the fundamental physical principles governing magnetic skyrmions or integrating those concepts with methods of detection, characterization and potential applications. Magnetic Skyrmions and their Applications delivers a coherent, state-of-the-art discussion on the current knowledge and potential applications of magnetic skyrmions in magnetic materials and device applications. First the book reviews key concepts such as topology, magnetism and materials for magnetic skyrmions. Then, charactization methods, physical mechanisms, and emerging applications are discussed. - Covers background knowledge and details the basic principles of magnetic skyrmions, including materials, characterization, statics and dynamics - Reviews materials for skyrmion stabilization including bulk materials and interface-dominated multilayer materials - Describes both well-known and unconventional applications of magnetic skyrmions, such as memristors and reservoir computing

This is a sequel to the World Scientific volume edited by Gerald E Brown in 1994 entitled “Selected Papers, with Commentary, of Tony Hilton Royle Skyrme”. There has been a series of impressive developments in the application of the skyrmion structure to wide-ranging physical phenomena. The first volume was mainly focused on the rediscovery of the skyrmion in 1983 in the context of Quantum Chromodynamics (QCD) and on its striking role in nuclear physics. Since 1994, skyrmions have been found to play an even greater role not only in various aspects of particle physics and astrophysics but also most remarkably in condensed matter physics. It is also proving to be fruitful in dense hadronic matter relevant to compact stars, a system difficult to access by other approaches. The recent discovery of holographic baryons in gravity/gauge duality which correspond to skyrmions in the infinite tower of vector mesons provides a valuable confrontation of string theory with nature, particularly in the regime of strong coupling that QCD proper has difficulty in accessing. This volume consists of contributions from the active researchers who have made important progress in these three areas of theoretical physics — condensed matter physics, nuclear and particle physics, and string theory.

Makes use of the first principle methods and associated analytic tools that are complementary to the majority of skyrmion literature that relies on phenomenological and numerical approaches Contains comprehensive background materials that are organized based on symmetry principles Puts together various interdisciplinary subjects in terms of a coherent language with clear illustrations and detailed comments so that readers can verify mathematical manipulations throughout the text

The energy cost associated with modern information technologies has been increasing exponentially over time, stimulating the search for alternative information storage and processing devices. Magnetic skyrmions are solitonic nanometer-scale quasiparticles whose unique topological properties can be thought of as that of a Mobius strip. Skyrmions are envisioned as information carriers in novel information processing and storage devices with low power consumption and high information density. As such, they could contribute to solving the energy challenge. In order to be used in applications, isolated skyrmions must be thermally stable at the scale of years. In this work, their stability is studied through two main approaches: the Kramers' method in the form of Langer's theory, and the forward flux sampling method. Good agreement is found between the two methods. We find that small skyrmions possess low internal energy barriers, but are stabilized by a large activation entropy. This is a direct consequence of the existence of stable modes of deformation of the skyrmion. Additionally, frustrated exchange that arises at some transition metal interfaces leads to new collapse paths in the form of the partial nucleation of the corresponding antiparticle, as merons and antimerons.

This brief reviews current research on magnetic skyrmions, with emphasis on formation mechanisms, observation techniques, and materials design strategies. The response of skyrmions, both static and dynamical, to various electromagnetic fields is also covered in detail. Recent progress in magnetic imaging techniques has enabled the observation of skyrmions in real space, as well as the analysis of their ordering manner and the details of their internal structure. In metallic systems, conduction electrons moving through the skyrmion spin texture gain a nontrivial quantum Berry phase, which provides topological force to the underlying spin texture and enables the current-induced manipulation of magnetic skyrmions. On the other hand, skyrmions in an insulator can induce electric polarization through relativistic spin-orbit interaction, paving the way for the control of skyrmions by an external electric field without loss of Joule heating. Because of its nanometric scale, particle nature, and electric controllability, skyrmions are considered as potential candidates for new information carriers in the next generation of spintronics devices.

' This book presents, in the form of reviews by world''s leading physicists in wide-ranging fields in theoretical physics, the influence and prescience of Skyrme''s daring idea of 1960, originally conceived for nuclear physics, that fermions can arise from bosons via topological solitons, pervasively playing a powerful role in wide-ranging areas of physics, from nuclear/astrophysics, to particle physics, to string theory and to condensed matter physics. The skyrmion description, both from gauge theory and from gauge/gravity duality, offers solutions to some long-standing and extremely difficult problems at high baryonic density, inaccessible by QCD proper. It also offers explanations and makes startling predictions for fascinating new phenomena in condensed matter systems. In both cases, what is at the core is the topology although the phenomena are drastically different, even involving different spacetime dimensions. This second edition has been expanded with addition of new reviews and extensively updated to take into account the latest developments in the field. Contents:Hadrons and Nuclear Matter:Skyrmions and Nuclei (R A Battye, N S Manton and P M Sutcliffe)States of Carbon-12 in the Skyrme Model (P H C Lau and N S Manton)Electromagnetic Form Factors of the Nucleon in Chiral Soliton Models (G Holzwarth)Exotic Baryon Resonances in the Skyrme Model (D Diakonov and V Petrov)Heavy-Quark Skyrmions (N N Scoccola)Pentaquark Candidates P+c(4380) and P+c(4450) within the Soliton Picture of Baryons (N N Scoccola, D O Riska and M Rho)Skyrmion Approach to Finite Density and Temperature (B-Y Park and V Vento)Fractionized Skyrmions in Dense Compact-Star Matter (M Harada, Y-L Ma, H K Lee and M Rho)The Skyrme Model in the BPS Limit (C Adam, C Naya, J Sánchez-Guillén, R Vazquez and A Wereszczyński)Superqualitons: Baryons in Dense QCD (D K Hong)Condensed Matter:Rotational Symmetry Breaking in Baby Skyrme Models (M Karliner and I Hen)Emergent Gauge Fields and Their Nonperturbative Effects in Correlated Electrons (K-S Kim and A Tanaka)Spin and Isospin: Exotic Order in Quantum Hall Ferromanets (S M Girvin)Noncommutative Skyrmions in Quantum Hall Systems (Z F Ezawa and G Tsitsishvili)Meron-Pair Excitations in Bilayer Quantum Hall System (K Moon)Spin and Pseudospin Textures in Quantum Hall Systems (H A Fertig and L Brey)Half-Skyrmion Theory for High-Temperature Superconductivity (T Morinari)Deconfined Quantum Critical Points (T Senthil, A Vishwanath, L Balents, S Sachdev and M P A Fisher)Skyrmions in a Density-Wave State: A Mechanism for Chiral Superconductivity (S Chakravarty and C-H Hsu)String Theory:Skyrmion and String Theory (S Sugimoto)Holographic Baryons (P Yi)The Cheshire Cat Principle from Holography (H B Nielsen and I Zahed)Baryon Physics in a Five-Dimensional Model of Hadrons (A Pomarol and A Wulzer)Holographic Skyrmions (P M Sutcliffe)Holographic Baryons and Instanton Crystal (V Kaplunovsky, D Melnikov and J Sonnenschein) Readership: Research scientists in the fields of condensed matter physics, nuclear and particle physics, and string theory. '

The December 1988 issue of the International Journal of Modern Physics A is dedicated to the memory of Tony Hilton Royle Skyrme. It contains an informative account of his life by Dalitz and Aitchison's reconstruction of a talk by Skyrme on the origin of the Skyrme model. From these pages, we learn that Tony Skyrme was born in England in December 1922. He grew up in that country during a period of increasing economic and political turbulence in Europe and elsewhere. In 1943, after Cambridge, he joined the British war effort in making the atomic bomb. He was associated with military projects throughout the war years and began his career as an academic theoretical physicist only in 1946. During 1946-61, he was associated with Cambridge, Birmingham and Harwell and was engaged in wide-ranging investigations in nuclear physics. It was this research which eventually culminated in his studies of nonlinear field theories and his remarkable proposals for the description of the nucleon as a chiral soliton. In his talk, Skyrme described the reasons behind his extraordinary sug gestions, which when first made must have seemed bizarre. According to him, ideas of this sort go back many decades and occur in the work of Sir William Thomson, who later became Lord Kelvin. Skyrme had heard of Kelvin in his youth.

This book presents both experimental and theoretical aspects of topology in magnetism. It first discusses how the topology in real space is relevant for a variety of magnetic spin structures, including domain walls, vortices, skyrmions, and dynamic excitations, and then focuses on the phenomena that are driven by distinct topology in reciprocal momentum space, such as anomalous and spin Hall effects, topological insulators, and Weyl semimetals. Lastly, it examines how topology influences dynamic phenomena and excitations (such as spin waves, magnons, localized dynamic solitons, and Majorana fermions). The book also shows how these developments promise to lead the transformative revolution of information technology.