Phase rigidity and h/2e oscillations in a single-ring Aharonov-Bohm experiment

We address the results presented recently by Yacoby er al. [Phys. Rev. Lett. 74, 4047 (1995)] on the coherency and phase evolution in a resonant tunneling quantum dot embedded in an Aharonov-Bohm (AB) ring. The observed phase rigidity of the AB conductance oscillations is theoretically explained by invoking simple symmetry arguments applicable to two terminal measurements, and is corroborated experimentally in generic experiments. We show that under certain conditions h/2e oscillations dominate completely the conductance of a single AB ring.