Near-field radiative heat transfer between two ?-quartz plates having hyperbolic and double-negative-permittivity bands

Near-field radiative heat transfer (NFRHT) between two semi-infinite alpha-quartz plates was theoretically in-vestigated based on the fluctuation-dissipation theorem. By setting the temperatures of the two alpha-quartz plates respectively equal to 300 K and 299 K, the near-field radiative heat flux (NFRHF) was calculated and compared with the cases of SiC and hexagonal boron nitride (hBN), considering the influence of optic axis (OA) orientation. The results show that the NFRHF between the two alpha-quartz plates can surpass 3 times that between two SiC plates and 7 times that between two hBN plates at a separation distance of 10 nm. This vastly enhanced NFRHT was attributed to excitation of phonon polaritons in the hyperbolic and double-negative-permittivity (DNP) bands of alpha-quartz. It is found that excited surface phonon polari-tons in DNP bands can be hyperbolic-like or elliptic-like, and the NFRHF in DNP bands contributes more than half of the total NFRHF for alpha-quartz. Furthermore, the hyperbolic and DNP bands that distribute in a wide frequency range give alpha-quartz the potential to achieve much higher NFRHF than using other materials such as SiC and hBN at different temperatures. Therefore, our work is helpful to deepen the understanding of surface polaritons in hyperbolic and DNP bands and their effect on NFRHT, which may be beneficial to design of energy transfer and conversion devices based on NFRHT.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, near-field radiative heat transfer between two semi-infinite alpha-quartz plates was theoretically investigated using the fluctuation-dissipation theorem. By comparing with SiC and hBN cases and considering the influence of optic axis orientation, it was found that the near-field radiative heat flux between the two alpha-quartz plates can surpass that of SiC and hBN. This enhanced heat transfer is attributed to the excitation of phonon polaritons in alpha-quartz, particularly in the hyperbolic and double-negative-permittivity bands. The research also revealed that surface phonon polaritons in the double-negative-permittivity bands contribute more than half of the total near-field radiative heat flux for alpha-quartz.