题 目：New analytic magnetic Skyrmion solutions
主讲人：Roberto Menta
单 位：意大利比萨高等师范大学
时 间：2024年11月27日 18:00
ZOOM：713 668 5659
密 码： 123456
摘 要：Magnetic Skyrmions are described by one control parameter (ϵ) and one length scale. In this talk, we investigate the two extreme limits of the control parameter, infinitely large and vanishing, and find that the magnetic Skyrmion becomes a "restricted" magnetic Skyrmion and an O(3) sigma model lump, respectively. Depending on the potential under consideration, the restricted limit manifests differently. In the case of the Zeeman term, the restricted magnetic Skyrmion becomes a "supercompacton" that develops a discontinuity, whereas for the Zeeman term to the power 3/2 it becomes a normal compacton. In both the lump and the restricted limit the solution is given in exact explicit form. We observe that the case of the Zeeman term squared, which can also be understood as a special combination of the Zeeman term and the easy-plane potential, the analytically exact solution for all values of the coupling, including the critical BPS case, is also of the lump type. Finally, we notice that certain materials (e.g., Fe1-xCoxSi or Mn1-xFexGe) have a rather large control parameter ϵ of order 100, making the restricted limit a suitable rough approximation. In the final part of the talk, I provide a brief overview of a recent generalization of magnetic skyrmions to three dimensions, extending their theoretical framework to an S3 target space with a four-dimensional magnetization vector. This higher-dimensional approach reveals rich solitonic physics. In the simplest model, incorporating exchange interaction, DMI, and an external potential, we identify a Skyrmion and a sphaleron. Adding the Skyrme term further enriches the spectrum, yielding a small metastable Skyrmion, an unstable sphaleron, and a large stable Skyrmion.
简 介：Roberto Menta is a PhD student at Scuola Normale Superiore, Pisa, Italy, and works on magnetic Skyrmions, quantum computing and spintronics. Roberto has recently published a paper in Phys.Rev.Research with his PhD advisors.
