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

Wide band shot noise, associated with d.c. current flow through a quan tum point contact (QPC), is measured in the microwave frequency range of 8-18 GHz. As the number of conducting channels in the QPC changes, the noise power oscillates, with almost zero value at the conductance plateaus. Consistent with existing theories the noise peaks depend lin early on the d.c. current. Surprisingly, however, in the pinch off reg ion, where QPC is expected to behave as a classical injector, we find strong noise suppression, possibly mediated by the Coulomb interaction in the QPC region.