Tuning of the transmission resonance in Aharonov-Bohm quantum rings

We investigate the total transmission probability of a nanoscale Aharonov-Bohm (AB) ring with an embedded quantum dot in one of its arms and a magnetic flux passing through its center. We find a peculiar quantum transport though this system such as a symmetric Breit- Wigner (BW) and an asymmetric Fano transmission resonance. The transition from BW to Fano resonance (or vice verse) occurs by tuning the magnetic AB flux threading through the AB ring, indicating the Fano asymmetric parameter is extended to a complex number. Unique properties of the AB phase coexistent with Fano interference are examined.