Optical magnetoelectric effect in multiferroic materials: Evidence for a Lorentz force acting on a ray of light

We theoretically propose that the optical analog of a Lorentz force acting on a ray of light is realized in multiferroic materials such as GaFeO3 showing the magnetoelectric effect. The toroidal moment (T) over right arrow=Sigma(j)(r) over right arrow (j) x (S) over right arrow (j) plays the role of a vector potential, while its rotation corresponds to a magnetic field for photons. Hence, the light is subject to the Lorentz force when propagating through the domain wall region of the ferromagnetic or ferroelectric order. A realistic estimate on the magnitude of this effect is given.