DYNAMICAL CONDUCTIVITY OF SINGLE-ELECTRON RESONANT-TUNNELING SYSTEMS OUT OF EQUILIBRIUM

The resonant tunneling under an a.c. bias superimposed on a d.c. volta ge through a semiconducting quantum dot is investigated. A single reso nant level is considered with Coulomb repulsion between electrons with opposite spins taken into account. Using the irreducible Green's func tions method in the Keldysh non-equilibrium form, the propagator of th e electrons in the well is obtained for the case of nonzero d.c. bias, assuming that transient processes due to the sudden switching-on of t he d.c. bias have decayed. The possibility of a Kondo peak appearing i n the density of states is discussed. The conductance and the energy l osses of the two-barrier system are calculated in the linear-response formalism. The results are interpreted from the viewpoint of the energ y spectrum of the well electrons which reflects the electron correlati ons (the finite value of the Coulomb repulsion).