  We present a non-perturbative calculation of indirect exchange interaction
between two paramagnetic impurities via 2D free carriers gas separated by a
tunnel barrier. The new method accounts for the impurity attractive potential
producing a bound state. The calculations show that for if the bound impurity
state energy lies within the energy range occupied by the free 2D carriers the
indirect exchange interaction is strongly enhanced due to resonant tunneling
and exceeds by a few orders of magnitude what one would expect from the
conventional RKKY approach.
