Sharpened Aharanov-Bohm oscillations near resonance in a balanced ring with double quantum dots

In a balanced Aharonov-Bohm ring with an identical quantum dot (QD) in each arm, the transmission amplitude near resonance consists of a zero and pole which can be made to nearly or exactly overlap in the complex-energy plane. This presents a sensitively balanced region of parameter space in which arbitrarily sharp transmission resonance spikes manifest. Analytical results based on a tight-binding solution of the Schrodinger Equation for this system demonstrate the extreme flux sensitivity of the balanced ring in the vicinity of the resonance near the quasi-bound state energy of the QD's. This effect may have practical applications as a sensitive monitor of magnetic flux.