  We consider the excitation of large amplitude gyrotropic vortex core
precession in a Permalloy nanodisk by the torques originating from the in-plane
microwave current flowing along the interface of the Permalloy/Bi$_2$Se$_3$
heterostructures, in which the huge charge-to-spin conversion ratio is observed
\cite{Mellnik-2014}. We consider analytically and by micromagnetic modelling
the dependence of this excitation on the frequency and magnitude of the
microwave current. The analogies of the vortex dynamics and the Landau phase
transitions theory is demonstrated. These findings open the possibility to
excite gyrotropic vortex motion with the current densities far lower than by
any other means.
