TEMPORALLY CORRELATED TRANSPORT AND SHOT-NOISE SUPPRESSION IN A BALLISTIC QUANTUM POINT-CONTACT

Wide-band shot noise, associated with DC current flow through a quantu m point contact (QPC), is measured in the microwave frequency range 8- 18 GHz. As the number of conducting channels in the QPC changes, the n oise power oscillates, with a value of almost zero at the conductance plateaux. Consistent with existing theories, the noise peaks depend li nearly on the DC current. Surprisingly, however, in the pinch-off regi on, where QPC is expected to behave as a classical injector, we find s trong noise suppression, possibly mediated by the Coulomb interaction in the QPC region.