Near-field radiative heat transfer between nonpolar epsilon-near-zero dielectric-filled Si gratings

Epsilon-near-zero (ENZ) materials have attracted significant attention in the far- and near fields of thermal radiation in recent years because of their unique optical characteristics. However, it is not considered an optimal carrier for near-field radiative heat transfer (NFRHT) due to the excessively low frustrated mode. In this paper, we address this drawback with a metamaterial composed of artificial hypothetical nonpolar ENZ dielectric-filled Si gratings. The behavior of NFRHT with ENZ has been investigated based on fluctuational electrodynamic and rigorous coupled-wave analysis. An artificial mode named Meta-NP ENZ mode is presented to reveal the significant enhancement of NFRHT, which can be demonstrated by the electric field intensity enhancement. Furthermore, we find that the increasing imaginary part may lead to an anomalous amplification of heat flux despite causing a recession in the Meta-NP ENZ mode, and this mode remains robust with respect to the plasma frequency shift of grating material. Our findings demonstrate that the ENZ dielectric exhibits outstanding performances similar to those observed in far-field radiation, surpassing the limitations of both Si gratings and nonpolar ENZ dielectric in NFRHT.