Modulational instability of a recent nonlinear plasmonic metamaterial:   Finite-difference-time-domain simulations
  By doing time-domain simulations, we find the proposal for negative-to-positive index switching proposed in [Physical Review Letters, 106 105503 (2012)] may be fragile. The negative opinion on the uniform switching of local optical constants in our recent paper [arXiv:1111.1476v2] based on the circuit model of metamaterials can therefore be verified in this specific and realistic case. 
Yi S. Ding, Jiasen Zhang and Ruo-Peng Wang
cond-mat.mtrl-sci cond-mat.mes-hall