We study transport at finite bias, i.e., beyond the linear regime, through two interacting resonant levels connected by a Fermi sea, by means of time-dependent density-matrix renormalization group. We first consider methodological issues, such as the protocol that leads to a current-carrying state and the characterization of the steady state. At finite sizes, both the current and the occupations of the interacting levels oscillate as a function of time. We determine the amplitude and period of such oscillations as a function of bias. We find that the occupations on the two dots oscillate with a relative phase which depends on the distance between the impurities and on the Fermi momentum of the Fermi sea, as expected for Rudermann-Kittel-Kasuya-Yosida interactions. Also, the approximant to the steady-state current displays oscillations as a function of the distance between the impurities. Such a behavior can be explained by resonances in the free case. We then discuss the incidence of interaction on such a behavior. We conclude by showing the effect of the bias on the current, making connection with the one-impurity case.

• Received 1 February 2013

DOI:https://doi.org/10.1103/PhysRevB.88.245105