Experiments on the Parallel Hall Effect in Three-Dimensional Metamaterials

The classical Hall effect in ordinary isotropic conducting materials describes the occurrence of a voltage perpendicular to the direction of the electric-current flow and perpendicular to the imposed magnetic-field vector. The Hall effect is routinely used in magnetic-field sensors. Here, we fabricate and characterize microstructured anisotropic metamaterials composed of a single semiconducting constituent (n-type ZnO) for which the direction and the sign of the Hall electric field can be tailored by microstructure. This class of metamaterials includes the possibility of a Hall voltage parallel-rather than perpendicular-to the magnetic-field vector. One possible future application arising from this far-reaching control of the effective electric-conductivity tensor is a sensor measuring the circulation of a magnetic field.