  We study dynamical mass generation and the resultant helical spin orders in
topological Dirac and Weyl semimetals, including the edge states of quantum
spin Hall insulators, the surface states of weak topological insulators, and
the bulk materials of Weyl semimetals. In particular, the helical spin textures
of Weyl semimetals manifest the spin-momentum locking of Weyl fermions in a
visible manner. The spin-wave fluctuations of the helical order carry electric
charge density; therefore, the spin textures can be electrically controlled in
a simple and predictable manner.
