The analogy between magnetism and electricity has long been established by Maxwell in the 19th century, in spite of their subtle difference. While magnetic materials display paramagnetism, ferromagnetism, antiferromagnetism, and diamagnetism, only paraelectricity, ferroelectricity, and antiferrolelectricity have been found in dielectric materials. The missing `diaelectricity may be found if there exists a material that has a dc-polarization opposing the electric field or a negative dielectric susceptibility epsilon-1, with epsilon being the real part of the relative dielectric constant. Both of these properties have been observed in nano-particle aggregates under a dc electric bias field at room temperature. A possible collective effect in the nano-particle aggregates is proposed to account for the observation. `Diaelectricity implies overscreening by polarization to the external charges. Materials with a negative static epsilon are expected to provide attraction to similar charges and unusual scattering to electromagnetic waves with possible profound implications for high temperature superconductivity and communication.
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