Drastic Changes in Dielectric Function of Silver Under dc Voltage
  Significant changes of the relative permittivity of a silver film have been detected using the surface plasmon resonance (SPR) method when a constant electric field is applied to a MDM (metal-dielectric-metal) nanostructure. The structure looks like a capacitor with a 177-nm dielectric corundum film placed between two silver films 49nm and 37nm thick. The effect manifests itself as a noticeable change of the reflectivity of the structure when the voltage of up to 30V is applied to the electrodes. We have a good agreement between the theory and experiment only if we suppose that the optical parameters of anode and cathode silver films change differently and the Al_2O_3 film absorbs the incident light. The refraction coefficient of the cathode silver layer is shown to become zero when the applied voltage is above 16V. 
B.V.Kryzhanovsky, A.N.Palagushkin, S.A.Prokopenko, A.P.Sergeev,   A.O.Melikyan
cond-mat.mtrl-sci physics.atom-ph physics.optics