  Dark energy and dark matter are the dominant sources in the evolution of the
late universe. They are currently only indirectly detected via their
gravitational effects, and there could be a coupling between them without
violating observational constraints. We investigate the background dynamics
when dark energy is modelled as exponential quintessence, and is coupled to
dark matter via simple models of energy exchange. We introduce a new form of
dark sector coupling, which leads to a more complicated dynamical phase space
and has a better physical motivation than previous mathematically similar
couplings.
