Optical momentum in negative-index media

The correct form of the energy-momentum tensor in a dielectric has been the subject of a controversy spanning the last hundred years. Three principal forms for the momentum, in particular, have been identified for dispersive media. These are the Abraham, Minkowski and canonical momenta. We investigate whether any of these forms can be distinguished by considering pulses of light incident on materials with a negative refractive index and find that, for such materials, the canonical momentum has a qualitatively different behaviour to the other two.