Quantum transport in an aharonov-bohm electron interferometer

We report experiments on quantum electron interferometers fabricated from GaAs/AlGaAs heterojunctions. In this kind of devices, an electron island with two nearly open constrictions is defined by etched trenches. In the quantum Hall (QH) regime, two counterpropagating edge channels are coupled by tunneling in the constrictions, thus forming a closed interference path. We observe periodic Aharonov-Bohm oscillations in the four-terminal magnetoresistance on the i = 1, 2 and 4 QH plateaus. The period of the oscillations ΔB scales with i so that iΔB = const = 2.7±0.1 mT. For i = 1, we determine the dependence of the area enclosed by the electron interference path on the front-gate voltage, and find a constant integrated compressibility of the island electron system with respect to the front gates. We further compare the experimental results with two classical electrostatics models of the electron density profile in the island.