  Motivated by the recent experimental observations on the skyrmion creation by
cutting chiral stripe domains under a current drive [Jiang {\emph{et al.}},
Science {\bf{349}}, 283 (2015)], we study the mechanism of skyrmion generation
by simulating the dynamics of stripe domains. Our theory for skyrmion
generation is based on the fact that there are two half skyrmions attached to
the ends of a stripe domain. These half skyrmions move due to the coupling
between the skyrmion topological charge and current. As a consequence, the
stripe domain is bent or stretched depending on the direction of motion of the
half skyrmions. For a large current, skyrmions are created by chopping the
stripe domains via strong bending or stretching. Our theory provides an
explanation to the experiments and is supported by the new experiments.
Furthermore, we predict that skyrmions can also be generated using a Bloch
stripe domain under a spin transfer torque which can be realized in B20
compounds.
