Nonequilibrium theory for a quantum dot with arbitrary on-site correlation strength coupled to leads

An analytical expression for the current through a single level quantum dot for arbitrary strength of the on-site electron-electron interaction is derived beyond mean-field theory. By describing the localized states in terms of many-body operators, the employed diagrammatic technique for strong coupling between localized and delocalized states enables inclusion of electron correlation effects into the description of the local dynamics, which provides transport properties that are consistent with recent experimental data.

Figure 1

(Color online) Transport characteristics of the QD for $\{{\epsilon }_0,k_{B}T\}∕{\Gamma }_0=\{3,0.014\}$ as $U\to \infty$, calculated within the HIA (dashed) and the loop correction (solid). (a) The differential conductance and (b) the current, as functions of the bias voltage.

Figure 2

(Color online) Transport characteristics of the QD for $\{{\epsilon }_0,U,k_{B}T\}∕{\Gamma }_0=\{5∕6,0.5,0.014\}$, calculated within the HIA (dashed) and the loop correction (solid). (a) The differential conductance and (b) the current, as functions of the bias voltage. The small ripples in the solid line in (a) are due to that $dJ∕dV$ is the numerical derivative of the calculated current.

Figure 3

(Color online) Population numbers for the states $N_p$, $p=0,\sigma ,2$ $(N_{\uparrow }=N_{\downarrow })$ (faint) and average population $⟨n_{\uparrow }+n_{\downarrow }⟩$ (bold) of the QD, as functions of the bias voltage calculated within the HIA (dashed) and loop correction (solid). Parameters the same as in Fig. 2.

Figure 4

(Color online) Transport characteristics of the QD coupled to one nonmagnetic lead $(p_L=0)$ and one half-metallic lead $(p_R=1)$ resulting from the HIA (a) and (c), and the loop correction (b) and (d). (a), (b) Population numbers $N_p$, $p=0,\sigma ,2$ (faint) and $⟨n_{\uparrow }+n_{\downarrow }⟩$ (bold). (c), (d) Differential conductance $(dJ∕dV)$. Insets show the $J\text{−}V$ characteristics of the system. Here, $\{{\epsilon }_0,U,k_{B}T\}∕{\Gamma }_0=\{-5,5,0.08\}$.