Aharonov–Bohm effect in GaAs/GaAlAs ring interferometers

Aharonov–Bohm magnetoconductance oscillations are investigated in shallow etched, ring shaped GaAs/GaAlAs devices. The devices are operated with a few propagating transverse modes in the arms of the ring. The magnetoconductance oscillations, which have a period ΔB=3.3 mT, are studied around zero magnetic field. At millikelvin temperature the amplitude of the oscillations is as large as 10% of the conductance, and they are observed at temperatures up to 8 K. The magnetoconductance oscillations shows phase-shifts and halving of the fundamental h/e periodicity as the electron density is varied globally by means of a Ti/Au topgate electrode. The findings are interpreted in terms of an asymmetry between the two arms of the ring. We demonstrate that the phase and shape of the AB oscillations is very sensitive to an asymmetry.