Fano versus Kondo Resonances in a Multilevel “Semiopen” Quantum Dot

Linear conductance across a large quantum dot via a single level ${ϵ}_0$ with large hybridization to the contacts is strongly sensitive to quasibound states localized in the dot and weakly coupled to ${ϵ}_0$. The conductance oscillates with the gate voltage due to interference of the Fano type. At low temperature and Coulomb blockade, Kondo correlations damp the oscillations on an extended range of gate voltage values, by freezing the occupancy of the ${ϵ}_0$ level itself. As a consequence, the antiresonances of Fano origin are washed out. The results are in good correspondence with experimental data for a large quantum dot in the semiopen regime.

Figure 1

Conductance versus gate voltage through QD for $\gamma =1$ with $U=0$ at $T=0$, showing various Fano $q$ parameters. In the inset, the Fano dip for $q=0$ appears with various values of $\zeta ={\Gamma }_L/{\Gamma }_R$.

Figure 2

Fano $q$ versus gate voltage $V_g$ for $\gamma =15$ levels: $U=0.1\mathrm{e}\mathrm{V}$ (oscillating solid curve); $U=0$ ( dashed line). The thick line is calculated for $U=0.1\mathrm{e}\mathrm{V}$ in the absence of interference due to the $\gamma$ levels. The inset shows the conductance for $\gamma =15$ and $U=0$.

Figure 3

Conductance versus gate voltage through the QD for $U=0.1\mathrm{e}\mathrm{V}$ at $T=0$ for different ratios of $({\Gamma }_L+{\Gamma }_R)/U$. See also the corresponding $T_K$ values in the inset of Fig. 4.

Figure 4

Conductance versus gate voltage through the QD for $U=0.1\mathrm{e}\mathrm{V}$ at various temperatures. The inset shows the dependence of $T_K$ on the ratio $\Gamma /U$ for the symmetric case ($V_g=0.05\mathrm{e}\mathrm{V}$), as obtained from the fitting to the Fermi liquid relation (see text).