  The low temperature electrical conductance through correlated quantum dots
provides a sensitive probe of the physics (e.g., of Fermi-liquid vs
non-Fermi-liquid behavior) of such systems. Here, we investigate the role of
level asymmetry (gate voltage) and local Coulomb repulsion (charging energy) on
the low temperature and low field scaling properties of the linear conductance
of a quantum dot described by the single level Anderson impurity model. We use
the numerical renormalization group to quantify the regime of gate voltages and
charging energies where universal Kondo scaling may be observed and also
quantify the deviations from this universal behavior with increasing gate
voltage away from the Kondo regime and with decreasing charging energy. We also
compare our results with those from a recently developed method for linear and
non-linear transport, which is based on renormalized perturbation theory using
dual fermions, finding excellent agreement at particle-hole symmetry and for
all charging energies and reasonable agreement at small finite level asymmetry.
Our results could be a useful guide for detailed experiments on conductance
scaling in semiconductor and molecular quantum dots exhibiting the Kondo
effect.
