Negative Static Dielectric Constant Under Electrical Field

We report the sign change of the dielectric constant ($\epsilon^\prime$) for the Ba-Ti-O based giant electrorheological (ER) fluid under the electrical field ($E$) up to 5 kV/mm. The data that extend to low frequency suggest that the static $\epsilon^\prime$ changes from positive to negative under the dc bias. Models that were suggested for the left-handed materials (LHM), e.g. resonance models and plasmon models, are examined. Our analysis suggests that the self- assembled nanostructures under the electrical field and a large suppression of carrier collisions play key roles. The great potential for application of this phenomena will be discussed.