MESOSCOPIC BEHAVIOR NEAR A 2-DIMENSIONAL METAL-INSULATOR-TRANSITION

We study conductance fluctuations in a two-dimensional electron system as a function of chemical potential (or gate voltage) from the strong ly insulating to the metallic regime. Power spectra of the fluctuation s decay with two distinct exponents (1/v(l) and 1/v(h)). For conductiv ity sigma similar to 0.1e(2)/h, we find a third exponent (1/v(i)) in t he shortest samples, and nonmonotonic dependence of v(i) and v(l) on s igma. We study the dependence of v(i), v(l) v(h), and the variances of corresponding fluctuations on sigma, sample size, and temperature, Th e anomalies near sigma similar or equal to 0.1e(2)/h indicate that the dielectric response and screening length are critically behaved, i.e. , that Coulomb correlations dominate the physics. [S0163-1829(97)50440 -1].