Half-quantum vortex and d-soliton in Sr${}_2$RuO${}_4$

Assuming that the superconductivity in Sr${}_2$RuO${}_4$ is described by a planar p-wave order parameter, we consider possible topological defects in Sr${}_2$RuO${}_4$. In particular, it is shown that both of the $\widehat{d}$-soliton and half-quantum vortex can be created in the presence of the magnetic field parallel to the $a$-$b$ plane. We discuss how one can detect the ${\hat d}$-soliton and half-quantum vortex experimentally.