Near-Field Radiative Heat Transfer between Black Phosphorus Sheets via Anisotropic Surface Plasmon Polaritons

Black phosphorus (BP), a novel natural two-dimensional layered material with intrinsic in-plane anisotropy, has been attracting significant research attention due to its outstanding electronic and optical properties and tunable bandgaps. Here, an enhancement of near-field radiative heat transfer (NFRHT) arising from a coupling of anisotropic surface plasmon polaritons (SPPs) between two layered BP sheets is demonstrated. The coupling of SPPs along armchair and zigzag directions dominate the NFRHT at near-infrared and mid-infrared frequencies, respectively. The dependence of NFRHT on the number of layers as well as the electron density of BP is then analyzed. It is found that at a small gap size the NFRHT between BP sheets with more number of layers and a higher electron density is lower. While this trend is reversed at a large gap size. Finally, the possibility of using BP to modulate the NFRHT by the mechanical rotation is explored. It is shown that the rotated system exhibits a nonmonotonic dependency of its heat transfer coefficient on the rotation angle, which has never been noted in the noncontact heat exchanges at nanoscale before. This work opens the possibility to apply BP-based materials for active thermal management at the nanoscale.