Antiresonances modulated by magnetic flux in an Aharonov-Bohm ring

With or without an inserted quantum dot or an attached side resonator, the transmission behavior of an Aharonov-Bohm (AB) ring Is investigated in the framework of quantum waveguide theory in the complex-energy plane. The calc ulated results show that the AB ring possesses antiresonances in the conduc tance and several kinds of transmission poles in the complex-energy plane. Piercing the ring, magnetic flux causes a series of crossovers among zero-p ole pairs. zero-double-pole pairs, peak-double-pole pairs, and peak-pole pa irs. With the inserted quantum dot or attached side resonator in one of its arms, the ring produces complicated behaviors in conductance: some of the poles are split into more than two parts. A kind of deformed Fano resonance is found in the conductance of the AB ring with the attached resonator. (C ) 1999 Published by Elsevier Science B.V. All rights reserved.