  We investigate theoretically the energy transfer phenomenon in a double-layer
graphene (DLG) system in which two layers are coupled due to the Coulomb
interlayer interaction without appreciable interlayer tunneling. We use the
balance equation approach and the dynamic and temperature dependent random
phase approximation (RPA) screening function in our calculations to obtain the
rates of energy transfer between two graphene layers at different layer
electron temperatures, densities and interlayer spacings and compare the
results with those calculated for the conventional double-layer two-dimensional
electron gas (2DEG) systems. In addition, we study the effect of changing
substrate dielectric constant on the rate of energy transfer. The general
behavior of the energy transfer rate in the DLG is qualitatively similar to
that obtained in the double-layer 2DEG but quantitatively its DLG values are an
order of magnitude greater. Also, at large electron temperature differences
between two layers, the electron density dependence of the energy transfer for
the DLG system is significantly different from that found for the double-layer
2DEG system, particularly in case of unequal layer electron densities.
