  We investigate the superradiance effects in three-dimensional topological
insulator HgTe with conducting surface states. We demonstrate that the
superradiance can be explained using the classical electrodynamic approach.
Experiments using the continuous-wave spectroscopy allowed to separate the
energy losses in the system into intrinsic and radiation losses, respectively.
These results demonstrate that the superradiance effects are not sensitive to
the details of the band structure of the material.
