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The Two‐Dimensional Electrides XONa (X=Mg, Ca) as Novel Natural Hyperbolic Materials
Author(s) -
Choe MyongIl,
Kim KwangHyon,
Wi JuHyok
Publication year - 2021
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000767
Subject(s) - materials science , metamaterial , electron , dielectric , free electron model , refraction , density functional theory , photonics , infrared , range (aeronautics) , reflection (computer programming) , condensed matter physics , optics , optoelectronics , physics , chemistry , computational chemistry , composite material , quantum mechanics , computer science , programming language
In two‐dimensional electrides, anionic electrons are spatially confined in interlayer regions with high density, comparable to metals, and they are highly mobile, just as free electrons, resembling hyperbolic metamaterials with metal‐dielectric multilayered structures. In this work, two‐dimensional electride materials MgONa and CaONa are proposed as good natural hyperbolic materials. By using the first‐principles calculations based on density functional theory (DFT), the electronic structures, stabilities, and optical properties of two‐dimensional electride materials XONa (X=Mg, Ca) are investigated. Our results show that they are stable in 1‐monolayer (1‐ML) structures as well as in bulk states. They exhibit hyperbolic dispersions from visible to near infrared spectral range with high qualities up to about 700, which is two orders‐of‐magnitude larger than the preceding bulk hyperbolic materials. Numerical results reveal that they exhibit negative refraction with low losses. Their high‐quality hyperbolic responses over a wide spectral range pave the way of broad photonic applications as natural hyperbolic materials.