Compendium of Natural Epsilon-Near-Zero Materials

Epsilon-near-zero (ENZ) materials are among the most intriguing electromagnetic materials, enabling the realization of electromagnetic field squeezing, wave steering, perfect absorption, and ultrafast optical switching. These phenomena arise from the strong interactions of light with substances with a near-zero real part of the permittivity and provide a new realm for fabricating optical and optoelectronic devices. However, ENZ materials are usually strongly dispersive, and their unique properties manifest only near certain optical wavelengths. Therefore, designing devices with targeted performance and operational wavelengths requires knowledge of the optical properties of a broad range of ENZ materials. Here, we present a comprehensive data set of natural materials, including metals, semiconductors, oxides, halides, and others, which exhibit intrinsic dielectric permittivity around zero. The data highlight the wavelength ranges over which the ENZ behavior occurs. Furthermore, we discuss application-specific quality factors and identify the most promising candidates for various applications across different spectral regions.