Near-field radiative thermal modulation between Weyl semimetal slabs

Abstract

We propose a thermal modulation structure composed of two identical Weyl semimetal (WSM) slabs separated by a nanoscale vacuum gap. Following Maxwell's equations and the dielectric tensor of the WSM, we derive the reflection matrix at the WSM/vacuum interface. Based on fluctuation electrodynamics, the effects of the Fermi level, the number of Weyl nodes, the separation between Weyl nodes and the thickness of vacuum gap on the heat transfer coefficient and the thermal modulation contrast are numerically discussed. It is found that the WSM possesses stronger near-field radiative ability in the low frequency region, where the coupled surface plasmon polaritons between the WSM slabs play a dominant role. By continuously tuning the Fermi level from 0.01 to 0.15 eV, a large modulation contrast as high as 58.5 is obtained at T = 300 K, while in the low temperature interval [50,160] K, the minimum modulation contrast can exceed 198 for a vacuum gap of 20 nm. The obtained results might be helpful in designing a WSM-based thermal modulator with giant modulation contrasts.