Abstract
We study the Hall coefficient over a wide temperature range in co-sputtered Cu
:
SiO
2 samples with metal volume fraction in the range of 0.45⩽
x⩽0.8. With decreasing metal volume fraction
x, the samples change from metal to insulator and the Hall coefficient
R increases drastically. A maximum has been observed at
x=0.51, which is ∼700 times larger than that at
x=0.8. This enhancement far exceeds the factor of 20, which can be derived from the classical percolation (finite size scaling) theory. Based on these observations, we conclude that the non-magnetic GHE arises most probably from quantum interference effects on the mesoscopic scale.