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

TL;DR

This study investigates conductance noise in doped silicon near the metal-insulator transition at low temperatures, revealing non-Gaussian fluctuations and divergence of noise magnitude as the transition is approached.

Contribution

It provides the first detailed analysis of non-Gaussian conductance fluctuations and their evolution across the metal-insulator transition in doped silicon at low temperatures.

Findings

Noise magnitude diverges as temperature decreases.

Distribution function becomes log-normal near the transition.

Strong non-Gaussian behavior observed below 20K.

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.