Aharonov-Bohm oscillation phase shift in a multi-terminal asymmetric quantum ring

We investigate coherent electron transport in a four-terminal asymmetric waveguide quantum ring with the focus on a controllable electrostatic Aharonov-Bohm (AB) oscillation phase shift. In the AlGaAs/GaAs device, electron wave interference has been detected in all possible four-terminal measurement configuration at a temperature as high as T = 1.5 K. We present a series of AB measurements in small magnetic fields for successive global gate voltages, which strongly suggest an electrostatic AB phase shift. Such a phase shift can be explained by the asymmetry of the ring and indicates that the design and positioning of voltage and current probes to the ring have a significant influence. (C) 2009 Elsevier B.V. All rights reserved.