Scaling properties of universal conductance fluctuations in quasiballistic split-gate wires: Probing geometrical effects.

Abstract

We have studied the universal conductance fluctuations observed in the low-temperature magnetoresistance of quasiballistic, split-gate quantum-wire structures. Since transport in such devices is determined by scattering from only a small number of impurities, it is of interest to know whether the fluctuations exhibit the same universal features characteristic of corresponding metallic systems. In this paper, we discuss results obtained in split-gate wire structures of two different lengths (L=2 and 6 \ensuremath{\mu}m). These indicate that, although the fluctuations scale qualitatively as expected as the system size is varied, the amplitude of the scaling, expressed via the adjustable constant \ensuremath{\beta}, is more than an order of magnitude smaller than the case for corresponding diffusive systems. We relate these features to the variation in the coherence area, the effective area over which electron interference takes place, for quasiballistic wire structures of different length and width.