  We investigate the quantum heat exchange between a nanojunction and a
many-body or electromagnetic environment far from equilibrium. It is shown that
the two-temperature energy emission-absorption mechanism gives rise to a giant
heat flow between the junction and the environment. We obtain analytical
results for the heat flow in an idealized high impedance environment and
perform numerical calculations for the general case of interacting electrons
and discuss the giant freezing and heating effects in the junction under
typical experimental conditions.
