Halfvortices in flat nanomagnets

TL;DR

This paper introduces halfvortices as a new type of topological defect in flat nanomagnets, highlighting their significance in the static and dynamic behavior of these systems, and relates them to similar phenomena in liquid crystal films.

Contribution

It identifies and characterizes halfvortices in nanomagnets, emphasizing their role alongside traditional vortices and linking them to domain walls and other topological defects.

Findings

Halfvortices manifest as edge kinks with bdbd winding.

Halfvortices are crucial for understanding nanomagnet statics and dynamics.

Domain walls contain multiple elementary halfvortices.

Abstract

We discuss a new type of topological defect in XY systems where the O(2) symmetry is broken in the presence of a boundary. Of particular interest is the appearance of such defects in nanomagnets with a planar geometry. They are manifested as kinks of magnetization along the edge and can be viewed as halfvortices with winding numbers \pm 1/2. We argue that halfvortices play a role equally important to that of ordinary vortices in the statics and dynamics of flat nanomagnets. Domain walls found in experiments and numerical simulations are composite objects containing two or more of these elementary defects. We also discuss a closely related system: the two-dimensional smectic liquid crystal films with planar boundary condition.