Influence of hBN orientation on the near-field radiative heat transfer between graphene/hBN heterostructures

Abstract

The influence of the optic axis orientation of hexagonal boron nitride (hBN) on the near-field radiative heat transfer between hBN slabs as well as between graphene/hBN heterostructures is studied. A modified 4 × 4 transfer matrix method is employed to calculate the near-field radiative heat flux (NFRHF) between the media. The numerical results show that the NFRHF will decrease when the optic axis of hBN is tilted off the direction of the energy flow for bare hBN slabs. The reason is that hyperbolic phonon polaritons excited in the hyperbolic bands of type I are largely suppressed for tilted optic axis, though surface phonon polaritons can be excited in the hyperbolic bands. On the contrary, the NFRHF between two graphene/hBN heterostructures is affected by the coupling of SPPs excited at the vacuum/graphene interface with those at the graphene/hBN interface and the formation of a hybrid mode, by which the NFRHF is maximum when the hBN slabs are arranged with strong in-plane anisotropy of the surface. The results obtained in this work may provide a promising way for manipulating near-field radiative heat transfer between anisotropic materials.