Current-voltage characteristics of a tunnel junction with resonant centers

We calculated the I-V characteristics of a tunnel junction containing impurities in the barrier. We consider the indirect resonant tunneling involving the impurities. The Coulomb repulsion energy Ec between two electrons with opposite spins simultaneously residing on the impurity is introduced by an Anderson Hamiltonian. At low temperatures T is much less than Ec the I-V characteristics is linear in V both for VEc and changes slope at V=Ec. This behaviour reflects the energy spectrum of the impurity electrons - the finite value of the charging energy Ec. At T ∼ Ec the junction reveals an ohmic-like behaviour as a result of the smearing out of the charging effects by the thermal fluctuations. (author). 10 refs, 2 figs