  The radiative heat transfer between two dielectrics can be strongly enhanced
in the near field in the presence of surface phonon-polariton resonances.
Nevertheless, the spectral mismatch between the surface modes supported by two
dissimilar materials is responsible for a dramatic reduction of the radiative
heat flux they exchange. In the present paper we study how the presence of a
graphene sheet, deposited on the material supporting the surface wave of lowest
frequency, allows to widely tune the radiative heat transfer, producing an
amplification factor going up to one order of magnitude. By analyzing the
Landauer energy transmission coefficients we demonstrate that this
amplification results from the interplay between the delocalized plasmon
supported by graphene and the surface polaritons of the two dielectrics. We
finally show that the effect we highlight is robust with respect to the
frequency mismatch, paving the way to an active tuning and amplification of
near-field radiative heat transfer in different configurations.
