  We theoretically study THz-light driven high-harmonic generation (HHG) in the
spin-liquid states of the Kitaev honeycomb model with a magnetostriction
coupling between spin and electric polarization. To compute the HHG spectra, we
numerically solve the Lindblad equation, taking account of the dissipation
effect. We find that isotropic Kitaev models possess a dynamical symmetry and
it is broken by a static electric field, analogous to HHG in electron systems.
We show that the HHG spectra exhibit characteristic continua of Majorana
fermion excitations and their broad peaks can be controlled by applying static
electric or magnetic fields. In particular, the magnetic-field dependence of
the HHG spectra drastically differ from those of usual ordered magnets. The
results indicate that intense THz laser provides a powerful tool to observe
dynamic features of quantum spin liquids.
