Epsilon-negative media from the viewpoint of materials science

A comprehensive review of the fundamentals and applications of epsilon-negative materials is presented in this paper. Percolative composites, as well as homogeneous ceramics or polymers, have been investigated to obtain the tailorable epsilon-negative properties. It's confirmed the anomalous epsilon-negative property can be realized in conventional materials. Meanwhile, from the perspective of materials science, the relationship between the negative permittivity and the composition and microstructure of materials has been clarified. It's demonstrated that the epsilon-negative performance is attributed to the plasmonic response of delocalized electrons within the materials and can be modulated by it. Moreover, the potential applications of epsilon-negative materials in electromagnetic interference shielding, laminated composites for multilayered capacitance, coil-less electric inductors, and epsilon-near-zero metamaterials are reviewed. The development of epsilon-negative materials has enriched the connotation of metamaterials and advanced functional materials, and has accelerated the integration of metamaterials and natural materials.