Near-field radiative heat transfer between shifted graphene gratings

We examine the near -field radiative heat transfer between finite -thickness planar fused silica slabs covered with graphene gratings, through the utilization of the Fourier modal method augmented with local basis functions (FMM-LBF), with a focus on the lateral shift effect (LSE). To do so, we propose and validate a minor modification of the FMM-LBF theory to account for the lateral shift. This approach goes far beyond the effective medium approximation, which cannot account for the lateral shift. We show that the heat flux can exhibit significant oscillations with the lateral shift, and at short separation, it can experience up to a 60-70% reduction compared with the aligned case. Such an LSE is found to be sensitive to the geometric factor d / D (separation distance to grating period ratio). When d / D > 1 (realized through large separation or small grating period), the two graphene gratings see each other as an effective whole rather than in detail, and thus, the LSE on heat transfer becomes less important. Therefore, we can clearly distinguish two asymptotic regimes for radiative heat transfer: the LSE regime, where a significant LSE is observed, and the non -LSE regime, where this effect is negligible. Furthermore, regardless of the lateral shift, the radiative heat flux shows a nonmonotonic dependence on the graphene chemical potential. That is, we can get an optimal radiative heat flux (peaking at similar to 0.3 eV chemical potential) by modulating the chemical potential in situ . This paper has the potential to unveil avenues for harnessing the LSE on radiative heat transfer in graphene-based nanodevices.