Theory of photon-assisted tunneling through quantum dot

Based on the two-channel Anderson Hamiltonian with the non-equilibrium electron distribution under an external electric field, we develop the theory of stationary photon-assisted tunneling current via strongly correlated energy levels in a quantum dot. The non-equilibrium (Mahanthappa–Baksi–Keldysh) Green function formalism is employed to study the Kondo effect and Coulomb blockade phenomenon in the presence of an external field. The Coulomb interaction is treated within the second order perturbation in the self-energy. The change of electron distribution function in the quantum dot due to emission and absorption of photons is taken into account and is found to play a very important role for the suppression of the Kondo effect. We show that an opening of new tunneling channel through photon side band accounts for a Coulomb staircase in the electric current.