Studies of h/e Aharonov-Bohm Photovoltaic Oscillations in Mesoscopic Au Rings

We have investigated a mesoscopic photovoltaic (PV) effect in micron-size Au rings in which a dc voltage Vdc is generated in response to microwave radiation. The effect is due to the lack of inversion symmetry in a disordered system. Aharonov-Bohm PV oscillations with flux period h/e have been observed at low microwave intensities for temperatures ranging from 1.4 to 13 K. For moderate microwave intensities the h/e PV oscillations are completely quenched providing evidence that the microwaves act to randomize the phase of the electrons. Studies of the temperature dependence of Vdc also provide evidence of the dephasing nature of the microwave field. A complete theoretical explanation of the observed behavior seems to require a theory for the PV effect in a ring geometry.