  Active control of heat flow is of both fundamental and applied interest in
thermal management and energy conversion. Here, we present a fluctuational
electrodynamic study of thermal radiation between twisted bilayer graphene
(TBLG), motivated by its unusual and highly tunable plasmonic properties. We
show that near-field heat flow can vary by more than 10-fold over only a few
degrees of twist, and identify special angles leading to heat flow extrema.
These special angles are dictated by the Drude weight in the intraband optical
conductivity of TBLG, and are roughly linear with the chemical potential.
Further, we observe multiband thermal transport due to the increasing role of
interband transitions as the twist angle decreases, in analogy to monolayer
graphene in a magnetic field. Our findings are understood via the surface
plasmons in TBLG, and highlight its potential for manipulating radiative heat
flow.
