  Optically-induced mechanical torque leading to the rotation of small objects
requires the presence of absorption or breaking cylindrical symmetry of a
scatterer. A spherical non-absorbing particle cannot rotate due to the
conservation of the angular momentum of light upon scattering. Here, we suggest
a novel physical mechanism for the angular momentum transfer to non-absorbing
particles via nonlinear light scattering. The breaking of symmetry occurs at
the microscopic level manifested in nonlinear negative optical torque due to
the excitation of resonant states at the harmonic frequency with higher
projection of angular momentum. The proposed physical mechanism can be verified
with resonant dielectric nanostructures, and we suggest some specific
realizations.
