Kondo Correlations and the Fano Effect in Closed Aharonov-Bohm Interferometers

Abstract

We study the Fano-Kondo effect in a closed Aharonov-Bohm (AB) interferometer which contains a single-level quantum dot and predict a frequency doubling of the AB oscillations as a signature of Kondo-correlated states. Using the Keldysh formalism, the Friedel sum rule, and the numerical renormalization group, we calculate the exact zero-temperature linear conductance $G$ as a function of the AB phase $\ensuremath{\phi}$ and level position $\ensuremath{\epsilon}$. In the unitary limit, $G(\ensuremath{\phi})$ reaches its maximum ${2e}^{2}/h$ at $\ensuremath{\phi}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\pi}/2$. We find a Fano-suppressed Kondo plateau for $G(\ensuremath{\epsilon})$ similar to recent experiments.