The Two-Dimensional Electrides XONa (X=Mg, Ca) as Novel Natural Hyperbolic Materials

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) electrides feature high-density, mobile anionic electrons in interlayer regions.
• These properties resemble hyperbolic metamaterials, which are typically artificial multilayer structures.

Purpose of the Study:

• To investigate the potential of 2D electride materials MgONa and CaONa as natural hyperbolic materials.
• To analyze their electronic structures, stability, and optical properties.

Main Methods:

• First-principles calculations based on density functional theory (DFT).
• Investigation of electronic band structures, stability of monolayer and bulk forms, and optical properties.

Main Results:

• MgONa and CaONa are stable in both 1-monolayer (1-ML) and bulk forms.
• These materials exhibit high-quality hyperbolic dispersions from the visible to near-infrared spectrum (quality factor up to ~700).
• Negative refraction with low optical losses was observed.

Conclusions:

• MgONa and CaONa function as effective natural hyperbolic materials.
• Their wide spectral range and high-quality hyperbolic response enable diverse photonic applications.