Transient current in a quantum dot subject to a change in coupling to its leads

The time-dependent non-crossing approximation is used to calculate the transient currents through a quantum dot in the Kondo regime subject to a sudden change in its coupling to the leads. The currents are found to display transient non-universal behaviour immediately after the perturbation and then to follow a slow universal increase toward equilibrium. The timescales for the approach to equilibrium are shown to be the same as those recently identified in a study of transient currents in a quantum dot subject to a sudden change in the energy of the dot level (Plihal et al 2005 Phys. Rev. B 71 165321). We present improved numerical algorithms which enable relatively fast calculation of the transient response of quantum dots to sudden perturbations