Many-body Correlation Effect on Mesoscopic Charge Relaxation

We investigate in a nonperturbative way the dynamics of a correlated quantum capacitor. We find that the many-body correlations do not disturb the universal low-frequency relaxation resistance per channel, $R_q(\omega=0) = h/4e^2$ ensured by the Korringa-Shiba rule whereas the interpretation of the quantum capacitance $C_q$ in terms of the density of states fails when strong correlations are present. The AC resistance $R_q(\omega)$ shows huge peaks (with values larger than $h/4e^2$) at $\hbar\omega \approx \pm \Gamma^*$, where $\Gamma^*$ is the renormalized level broadening. These peaks are merged to a single one at $\omega=0$ when a finite Zeeman field is applied comparable to $\Gamma^*$. The observed features of $R_q$, being most evident in the Kondo regime, are attributed to the generation of particle-hole excitations in the contacts accomplished by spin-flip processes in the dot.