Tunable Fano-Kondo effect in a quantum dot with an Aharonov-Bohm ring

We report experimental results and a theoretical model of the Fano-Kondo effect in a quantum dot embedded in an Aharonov-Bohm (AB) ring. A clear Fano-Kondo lineshape is observed in the coherent conductance as a function of the dot gate voltage. And the phase shift locking to pi/2, which is a touchstone of the SU(2) Kondo theory is clearly observed in the middle of Kondo valleys. The variation of the lineshape versus the magnetic flux piercing the ring is similar to that expected for a simple double-slit system rather than that under "phase rigidity" for two-terminal quantum interference devices. We have extended the theoretical model of single-channel AB ring to that of a multi-channel case and succeeded to explain the above puzzling results. This demonstrates that useful information can be extracted even from transport through two terminal devices. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.