Skyrmion

by Mannque Rho (Author), Ismail Zahed (Editor)

This book focuses on the characterisation of the chiral and topological nature of magnetic skyrmions in noncentrosymmetric helimagnets. In these materials, the skyrmion lattice phase appears as a long-range-ordered, close-packed grid of nearly millimetre-level correlation length, while the size of a single skyrmion is 3–100 nm. This is a very challenging range of length scales (spanning 5 orders of magnitude from tens of nm to mm) for magnetic characterisation techniques, and, to date, extensive information on this fascinating, magnetically ordered state has remained elusive.

This thesis presents significant advances in the imaging and theory of the ultrafast dynamics of surface plasmon polariton fields. The author details construction of a sub-10 femtosecond and sub-10 nanometer spatiotemporal resolution ultrafast photoemission microscope which is subsequently used for the discovery of topological meron and skyrmion-like plasmonic quasiparticles. In particular, this enabled the creation of movies of the surface plasmon polariton fields evolving on sub-optical wavelength scales at around 0.1 femtosecond per image frame undergoing vortex phase evolution.

This is a monograph on geometrical and topological features which arise in quantum field theory. It is well known that when a chiral fermion interacts with a gauge field we have chiral anomaly which corresponds to the fact that divergence of the axial vector current does not vanish. It is observed that this is related to certain topological features associated with the fermion and leads to the realization of the topological origin of fermion number as well as the Berry phase. The role of gauge fields in the quantization procedure has its implications in these topological features of a fermion and helps us to consider a massive fermion as a soliton (skyrrnion). In this formalism chiral anomaly is found to be responsible for mass generation. This has its relevance in electroweak theory where it is observed that weak interaction gauge bosons attain mass topologically.