Width of the charge-transfer peak in the SU(N) impurity Anderson model and its relevance to non-equilibrium transport

Abstract

We calculate the width $2Δ_{\text{CT}}$ and intensity of the charge-transfer peak (the one lying at the on-site energy $E_d$) in the impurity spectral density of states as a function of $E_d$ in the SU($N$) impurity Anderson model (IAM). We use the dynamical density-matrix renormalization group (DDMRG) and the noncrossing-approximation (NCA) for $N$=4, and a 1/$N$ variational approximation in the general case. In particular, while for $E_d \gg Δ$, where $Δ$ is the resonant level half-width, $Δ_{\text{CT}}=Δ$ as expected in the noninteracting case, for $-E_d \gg N Δ$ one has $Δ_{\text{CT}}=NΔ$. In the $N$=2 case, some effects of the variation of $% Δ_{\text{CT}}$ with $E_d$ were observed in the conductance through a quantum dot connected asymmetrically to conducting leads at finite bias [J. Könemann \textit{et al.}, Phys. Rev. B \textbf{73}, 033313 (2006)]. More dramatic effects are expected in similar experiments, that can be carried out in systems of two quantum dots, carbon nanotubes or other, realizing the SU(4) IAM.