  When circularly polarized wave scatters off a sphere, the scattered field
forms a vortex with spiraling energy flow. This is due to the transformation of
spin angular momentum into orbital one. Here we demonstrate that during this
scattering an anomalous force can be induced that acts in a direction
perpendicular to the propagation of incident wave. The appearance of this
lateral force is made possible by the presence of an interface in the vicinity
of scattering object. Besides radiation pressure and tractor-beam pulling
forces, this lateral force is another type of non-conservative force that can
be produced with unstructured light beams.
