Super‐Mossian Dielectrics for Nanophotonics

Abstract

Thus, semiconductors with high refractive index and negligible absorption losses in their sub-bandgap region are ideal materials for nanophotonics.Broadly speaking, the sub-bandgap refractive index of semiconductors trades off with its bandgap or absorption edge as shown in Figure 1. Hence at any given wavelength of operation, the maximum refractive index possible appears limited. This trade-off law is popularly known as the Moss rule. The Moss rule, which relates the sub-bandgap refractive index (n) of semiconductors to their bandgaps (E g ), is commonly stated as n 4 • E g ≈ 95 eV. Figure 1a plots the refractive index of common materials versus their bandgap with the Moss rule as a benchmark. While many of the materials do follow the trend predicted by the Moss rule, there are materials that fall significantly outside of this trend. Here, we refer to materials with refractive index appreciably higher than the prediction from the commonly known form of Moss rule as super-Mossian materials.Super-Mossian materials may be easily identified in Figure 1b plotting index versus bandgap but normalized by the Moss rule. There are many materials that outperform Moss rule, some by nearly 40%. Silicon, a popular high index dielectric in nanophotoics, beats the Moss' rule by only 20%. On the other hand, many well-known transition metal dichalcogenides (TMDCs) are super-Mossian in their bulk form and beat the Moss' rule by a wider margin. FeS 2 or iron pyrite is one such an outstanding super-Mossian material with its sub-bandgap refractive index nearly 40% higher than the Moss rule's prediction. Here, we focus on FeS 2 as an example super-Mossian material for high-index nanophotonics. To demonstrate the potential for super-Mossian materials, we grew FeS 2 thin-films and characterized the optical properties to show that the refractive index ranges from 4.2 to 4.4 in the infrared with an optical bandgap of 1.03 eV. Using optical grade FeS 2 , we experimentally demonstrated for the first time an all-dielectric metasurface based on this super-Mossian dielectric material. Searching for Super-Mossian MaterialsA common empirical rule relating the bandgap was first developed by Moss, which found that the bandgap and refractive index are related through n 4 • E g ≈ Constant with a phenomenological constant of 95 eV. [8] An approximate, order-of-magnitude derivation is as follows. We model the relative permittivity of

Multipole Mie Resonances in MXene-Antenna Arrays

“…Quantitative comparison of metasurface performance is further complicated by the vast differences in material properties and their responses to electromagnetic fields. The Moss rule, often employed to estimate the refractive index of a material, relies on the assumption that the refractive index scales with the static dielectric constant . However, this rule is limited to specific materials and does not hold true for all cases.…”

“…However, this rule is limited to specific materials and does not hold true for all cases. Iron pyrite exhibits a high refractive index, making it interesting for certain optical applications and as a candidate material for metasurfaces and photonic devices. , Consequently, comparing metasurfaces made of different materials, such as silicon, III–V compounds, and MXene, becomes exceedingly challenging due to their disparate behaviors and unique characteristics.…”

“…The Moss rule, often employed to estimate the refractive index of a material, relies on the assumption that the refractive index scales with the static dielectric constant. 60 However, this rule is limited to specific materials and does not hold true for all cases. Iron pyrite exhibits a high refractive index, making it interesting for certain optical applications and as a candidate material for metasurfaces and photonic devices.…”

Metasurface engineering for collective resonances, tailored emissivity, and enhanced photodetectors

“…This effect aligns with the principle of strong light confinement, where higher refractive indices lead to more confined modes. Super-Mossian materials, 13 such as silicon and iron pyrite, amplify this phenomenon, facilitating effective light manipulation within subwavelength structures and offering new prospects for cutting-edge nanophotonic functionalities.…”