-20 October 2005 -

Insulated TGG demonstrates phonon Hall effect

The phonon Hall effect or the acoustic equivalent of the electrical Hall effect, has been observed by physicists at the Max Planck Institut fur Festkorperforschung (MPI) and the Centre National de la Recherche Scientifique (CNRS) in France.

In the electrical Hall effect, when an electrical current (consisting of free electrons moving along a material sample) being driven by an electric field is subjected to an external magnetic field, the charge carriers will feel a force perpendicular to both the original current and the magnetic force, causing the electrical current to be deflected somewhat to the side.

Thermal transport is more complicated than electrical transport. A "current" of heat can consist of free electrons carrying thermal energy or it can consist of phonons, which are vibrations rippling through the lattice of atoms of the sample.

MPI-CNRS researchers believed that a magnetic deflection of phonons was possible, and have now demonstrated it experimentally in insulating samples of Terbium Gallium Garnet (a material often used for its magneto optical properties) where no free charges are present.