Electrostatically defined heterojunction rings and the Aharonov–Bohm effect

Abstract

Micron-sized loops of high-mobility two-dimensional electron gas have been made on GaAs-AlGaAs heterostructures using a novel split-gate technique. Aharonov–Bohm oscillations of amplitude up to 20% of the device resistance have been observed at very low temperatures (T<100 mK), together with h/2e oscillations which appear to be due to interference between pairs of time-reversed paths near B=0. The h/e period is found to vary by ∼25% with magnetic field, possibly as a result of the formation of edge states. In the quantum Hall effect, plateaus in Rxx are seen at high B due to variations in carrier concentration across the ring, which may cause backscattering of some edge states.