Negative Refraction in the Visible and Strong Plasmonic Resonances in Photonic Structures of the Electride Material Mg2N

Natural hyperbolic materials have recently attracted great attention due to their capability of supporting spatial mode frequency much higher than artificial metamaterials and the advantage that they do not require nanofabrication processes. For practical applications, however, hyperbolic bulk materials with lower optical losses in shorter wavelength range should be developed. This work presents the electronic structure and dielectric response of an electride Mg2N, revealing that this material exhibits hyperbolic responses with low optical loss in the visible and plasmonic responses with high‐quality in the near‐infrared range. Negative refraction in the red spectral range has been analytically and numerically demonstrated. In particular, nanoantenna structures of Mg2N generate strong plasmonic resonances in the near‐infrared and the intensity enhancement in the gap region is one order of magnitude higher compared with silver nanoantenna due to its much higher quality factor, which can find potential applications for nanoplasmonic purposes such as single molecule detections by surface‐enhanced hyper‐Raman spectroscopy and nonlinear wavelength generations at the nanoscale. As an electride material, Mg2N is revealed to exhibit a hyperbolic dispersion in the visible and plasmonic responses in the near‐infrared region by using ab initio calculations. Low‐loss negative refraction in the red spectral range and strong enhancement of hyper‐Raman scattering for single‐molecule detection explicitly show the advantages of this material.