Vector solitons in nonlinear isotropic chiral metamaterials
  Starting from the Maxwell equations, we used the reductive perturbation method to derive a system of two coupled nonlinear Schr\"{o}dinger (NLS) equations for the two Beltrami components of the electromagnetic field propagating along a fixed direction in an isotropic nonlinear chiral metamaterial. With single-resonance Lorentz models for the permittivity and permeability and a Condon model for the chirality parameter, in certain spectral regimes, one of the two Beltrami components exhibits a negative real refractive index when nonlinearity is ignored and the chirality parameter is sufficiently large.We found that, inside such a spectral regime, there may exist a subregime wherein the system of the NLS equations can be approximated by the Manakov system. Bright-bright, dark-dark, and dark-bright vector solitons can be formed in that spectral subregime. 
N. L. Tsitsas, A. Lakhtakia and D. J. Frantzeskakis
nlin.PS physics.optics