Optical Hall Effect

Physicists in Japan have theoretically shown that an optical equivalent of the Hall effect exists, and that this hypothesis could be borne out with experiments with polarized light.

In the classic Hall effect, an electric current, pulled along a conductor by an electric field, will be deflected sideways somewhat if in addition a magnetic field (perpendicular to the electric field and to the plane of the conductor) is applied. One can attribute to the sideways motion a "Hall voltage" and a "Hall resistance."

If the experimental conditions are even more stringent---extremely cold temperatures and high magnetic field---a quantum equivalent of the Hall effect manifests itself. In this case the electrons execute trajectories that are quantized; that is, the Hall resistance can take only certain discrete values.

Something like this might be happening when a light ray moves from one medium into another. The amount of the shift sideways at the deflection will depend on the change in the index of refraction from the one medium into the other.

Masaru Onoda (m.onoda@aist.go.jp, 81-29-861-2985) at the National Institute of Advanced Industrial Science and Technology (Tsukuba, Japan) and his colleagues at the University of Tokyo believe that the topological aspects of light refraction in materials can be explored in upcoming experiments using photonic crystals. In effect, they are predicting a correction to Snell's law for spin-polarized light. (Onoda et al., Physical Review Letters, upcoming article.)