Kondo and anti-Kondo resonances in transport through nanoscale devices

We study the current through a quantum wire side coupled to a quantum dot, and compare it with the case of an embedded dot. The system is modeled by the Anderson Hamiltonian for a linear chain, with one atom either coupled to (side-dot) or substituted by (embedded dot) a magnetic impurity. For realistic (small) hopping of the dot to the rest of the system, an exact relationship between both conductivities holds. We calculate the temperature dependence for moderate values of the Coulomb repulsion U using an interpolative perturbative scheme. For sufficiently large U and temperature greater than the Kondo temperature, the conductance as a function of gate voltage displays two extrema.