Observation of quantum asymmetry in an Aharonov-Bohm ring

Abstract

We have investigated the Aharonov-Bohm effect in a one-dimensional $\mathrm{GaAs}/{\mathrm{Ga}}_{0.7}{\mathrm{Al}}_{0.3}\mathrm{As}$ ring at low-magnetic fields. The oscillatory magnetoconductance of these systems is systematically studied as a function of density. We observe phase shifts of \ensuremath{\pi} in the magnetoconductance oscillations, and halving of the fundamental $h/e$ period, as the density is varied. Theoretically we find agreement with the experiment, by introducing an asymmetry between the two arms of the ring.