Bifurcation of a topological skyrmion string
Jing Xia, Xichao Zhang, Oleg A. Tretiakov, H. T. Diep, Jinbo Yang, Guoping Zhao, Motohiko Ezawa, Yan Zhou, Xiaoxi Liu
Abstract
Manipulation of three-dimensional (3D) topological objects is of both fundamental interest and practical importance in many branches of physics. We show by spin dynamics simulations that the bifurcation of a 3D skyrmion string in a layered frustrated system could be induced by the dampinglike spin-orbit torque. The bifurcation of a skyrmion string happens when the skyrmion string carries a minimal topological charge of $Q=2$. We demonstrate that three types of bifurcations could be realized by applying different current injection geometries, which lead to the transformation from I-shaped skyrmion strings to Y-, X-, and O-shaped ones. Besides, different branches of a bifurcated skyrmion string may merge into an isolated skyrmion string spontaneously. The mechanism of bifurcation should be universal to any skyrmion strings with $Q\ensuremath{\ge}2$ in the layered frustrated system and could offer a general approach to manipulate 3D stringlike topological objects for spintronic functions.