  Multiferroic hexagonal RMnO3 (R=rare earths) crystals exhibit dense networks
of vortex lines at which six domain walls merge. While the domain walls can be
readily moved with an applied electric field, the vortex cores were so far
impossible to control. Our experiments demonstrate that shear strain induces a
Magnus-type force pulling vortices and antivortices in opposite directions and
unfolding them into a topological stripe domain state. We discuss the analogy
between this effect and the current-driven dynamics of vortices in
superconductors and superfluids.
