Generalized Superconductors and Holographic Optics - II
  Using linear response theory, we analyze optical response properties of generalized holographic superconductors, in AdS-Schwarzschild and single R-charged black hole backgrounds in four dimensions. By introducing momentum dependent vector mode perturbations, the response functions for these systems are studied numerically, including the effects of backreaction. This complements and completes the probe limit analysis for these backgrounds initiated in our previous work ({\tt arXiv : 1305.6273}). Our numerical analysis indicates a negative Depine-Lakhtakia index for both the backgrounds studied, at low enough frequencies. The dependence of the response functions on the backreaction parameter and the model parameters are established and analyzed with respect to similar backgrounds in five dimensions. 
Subhash Mahapatra
hep-th