Nonequilibrium conductance of asymmetric nanodevices in the Kondo regime

The scaling properties of the conductance of a Kondo impurity connected to two leads that are in or out of equilibrium has been extensively studied, both experimentally and theoretically. From these studies, a consensus has emerged regarding the analytic expression of the scaling function. The question addressed in this Brief Report concerns the properties of the experimentally measurable coefficient alpha present in the term describing the leading dependence of the conductance on eV/T(K), where V is the source-drain voltage and T(K) is the Kondo temperature. We study the dependence of alpha on the ratio of the lead-dot couplings for the particle-hole symmetric Anderson model and find that this dependence disappears in the strong-coupling Kondo regime in which the charge fluctuations of the impurity vanish.