Conductance in very clean quantum wires and rings

We have observed clear Aharonov–Bohm oscillations in single and multiply connected rings with up to 20% modulation in conductance. The oscillations persist over a very wide range of conductance (0.1–2.0 e2/h) controlled with a gate. Conductance steps as a function of gate bias are observed for the first time in relatively long single and multiple parallel wires and rings. In 2–4 μm long wires, the conductance steps are in multiples of 2e2/h. In the case of the rings, steps of 0.8 and 1.2 e2/h are observed in one and two loops, respectively.