Toroidal Dipolar Response in a Metamaterial

See allHide authors and affiliations

Science  04 Nov 2010:
DOI: 10.1126/science.1197172


Toroidal multipoles are fundamental electromagnetic excitations different from those associated with the familiar charge and magnetic multipoles. They have been held responsible for parity violation in nuclear and particle physics, but direct evidence of their existence has remained elusive. We report on the observation of a resonant electromagnetic response in an artificially engineered medium, or metamaterial, which cannot be attributed to magnetic or charge multipoles and can only be explained by the existence of a toroidal dipole. Our direct experimental evidence of the toroidal response brings attention to the often-ignored electromagnetic interactions involving toroidal multipoles, which could be present in naturally occurring systems, especially at the macromolecule level, where toroidal symmetry is ubiquitous.