BREAKDOWN OF CORRELATED DIFFUSION IN QUASI-BALLISTIC QUANTUM WIRES ATHIGH MAGNETIC-FIELDS

We study the universal conductance fluctuations (UCF) observed in the low-temperature magnetoconductance of high-mobility GaAs/AlxGa1-xAs qu antum wires. As the magnetic field is increased, such that the cyclotr on orbit becomes smaller than the wire width, both the amplitude delta g and correlation field B-c of the fluctuations are found to increase linearly with magnetic field. The linear increase in B-c is in agreem ent with the results of recent nonlocal studies of the UCF,and is thou ght to demonstrate a transition to edge-related transport. Similarly, the increase in delta g is argued to result from a magnetically induce d breakdown of correlated diffusion, which occurs as the edge states b egin to be resolved. Such a breakdown was ndt observed in previous stu dies of dirty wires, in which the electron motion remains diffusive up to very high fields, but is instead thought to result from the quasib allistic nature of the wires we study.