CONDUCTANCE FLUCTUATIONS IN MESOSCOPIC QUANTUM WIRES NEAR THE BALLISTIC REGIME

Conductance fluctuations in mesoscopic quantum wires are studied numerically by the transfer matrix method together with the Landauer formula. Results show that the conductance fluctuations never decrease monotonically to zero towards the ballistic regime, but increase initially beyond the universal value and then decrease to zero making peak structures. Peak values are enhanced by the anisotropy of the band structure and the increasing wire width and the strength of impurity potential. The appearance of peak structures is considered due to the competition between the increase in the number of effective channels brought by the breakdown of the Ohm's law and the decrease in fluctuations of transmission probabilities. In the very ballistic regime, where the latter dominates fluctuations, a perturbative calculation is also performed to see how the fluctuations decrease. The results are in good agreement with numerical results.