Magnetic D-brane solitons: skyrmion strings ending on a Néel wall in chiral magnets

Abstract

Magnetic skyrmions extended to three dimensions form string-like objects whose fundamental role remains largely unexplored. We show that skyrmion strings can terminate on a Néel-type domain wall (DW), realizing a magnetic analogue of a Dirichlet(D)-brane soliton. While an isolated Néel DW tends to rotate into a Bloch DW, the Néel DW is stabilized when a skyrmion string ends on it, by being transformed into a trumpet. Unlike field-theory D-branes, the Bloch-type DMI produces linear rather than logarithmic DW bending, and the strings retain finite width far from the DW, circumventing singular behavior. Furthermore, the repulsive interaction between strings allows periodic multi-junction solutions, yielding a square lattice of alternating strings and local DW deformations as well as separating Bloch points. These results establish magnetic skyrmion strings as fundamental strings that can end on a D-brane.