Observation of non-gaussian conductance fluctuations at low temperatures in Si:P(B) at the metal-insulator transition

Abstract

We report investigations of conductance fluctuations (noise) in doped silicon at low temperatures (T$<20$K) as it is tuned through the metal-insulator transition (MIT). The scaled magnitude of noise, ${\gamma }_H$, increases with decrease in T following an approximate power law ${\gamma }_H\sim T^{-\beta }$. At low T, ${\gamma }_H$ diverges as $n/n_c$ crosses 1 from the metallic side. We find that the distribution function and second spectrum of the fluctuations show strong non-gaussian behavior below 20K as $n/n_c$ decreases through 1. In particular, the observed distribution function which is gaussian for $n/n_c>>1$, develops a log-normal tail as the transition is approached from the metallic side and eventually it dominates in the critical region.

9 pages, 5 figures