Negative refraction in gyrotropic media

The gyrotropy (chirality) as one of the manifestations of spatial dispersion responsible, e.g., for the rotation of the plane of polarization of light can also lead to negative refraction (NR) in certain frequency ranges. We discuss this effect for homogeneous isotropic chiral media in a nonresonant frequency domain close to frequency ${\omega }_L$ of longitudinal excitations, where dielectric permittivity vanishes: $ϵ\left({\omega }_L\right)=0$. Basic phenomena of reflection and refraction at the boundary of a chiral medium are considered and NR is demonstrated for frequencies below ${\omega }_L$ as following from the negative group velocity of circularly polarized electromagnetic waves of one handedness. We show that specular reflection of the polarized waves should provide a means of direct experimental detection of this frequency domain. We also discuss dissipation-related limitations for realization of NR.