Epsilon-near-zero characteristics of near-field radiative heat transfer between α-MoO 3 slabs.

Epsilon-near-zero (ENZ) materials, which manifest a wealth of exotic optical characteristics, have attracted significant research interest in recent years. However, these characteristics have rarely been considered in the study of near-field radiative heat transfer (NFRHT). In this work, we investigated the ENZ characteristics of the NFRHT between two symmetric biaxial α-MoO 3 slabs. The numerical results show that the NFRHT is greatly enhanced around the ENZ frequency of 1.604 × 10 14 rad s -1 . Notably, near the other two ENZ frequencies (1.832 × 10 14 rad s -1 and 1.891 × 10 14 rad s -1 ), only the NFRHT between α-MoO 3 slabs of certain thicknesses is enhanced. The reasons can be explained by the fact that the VHPs can be excited in almost all azimuthal angles at angular frequencies of 1.604 × 10 14 rad s -1 and 1.891 × 10 14 rad s -1 . For the ENZ frequency of 1.832 × 10 14 rad s -1 , the VHPs can be excited at the top and bottom, while the SHPs excited at the left and right sides. It is worth noting that both the hyperbolic and ENZ characteristics affect the NFRHT between α-MoO 3 slabs. Moreover, the excitation is strongly dependent on the thickness of the slab. Our findings contribute to understanding the physical mechanisms underlying the characteristics of the NFRHT at ENZ frequencies.