  It was shown that tunneling current flowing through a system with Coulomb
correlations leads to charge redistribution between the different localized
states. Simple model consisting of two electron levels have been analyzed by
means of Heisenberg motion equations taking into account all order correlations
of electron filling numbers in localized states exactly. We consider various
relations between Coulomb interaction and localized electron energies. Sudden
jumps of electron density at each level in a certain range of applied bias have
been found. We found that for some parameter range inverse occupation in the
two-level system appeared due to Coulomb correlations. It was shown also that
Coulomb correlations lead to appearance of negative tunneling conductivity at
certain relation between the values of tunneling rates from the two electronic
levels.
