  In this Letter, we develop an electrostatic theory for designing bulk
composites with effective lossless negative permittivities. The theory and
associated design procedure are validated by comparing their predictions with
those of rigorous full-wave simulations. It is demonstrated that the excitation
of the Frohlich mode (the first-order surface mode) of the constitutive
nanoparticles plays a key role in achieving negative permittivities with
compensated losses.
