We report investigations of conductance fluctuations (with $1/f^{\alpha }$ power spectra) in doped silicon at low temperatures ($T<20\mathrm{K}$) as it is tuned through the metal-insulator transition (MIT) by changing the carrier concentration $n$. The scaled magnitude of noise, ${\gamma }_{\mathrm{H}}$, increases with decreasing $T$ following an approximate power law ${\gamma }_{\mathrm{H}}\sim T^{-\beta }$. At low $T$, ${\gamma }_{\mathrm{H}}$ diverges as $n$ decreases through the critical concentration $n_{\mathrm{c}}$, accompanied by a growth of low-frequency spectral weight. The second spectrum and probability density of the fluctuations show strong non-Gaussian behavior below 20 K as $n/n_{\mathrm{c}}$ decreases through 1. This is interpreted as the onset of a glassy freezing of the electronic system across the MIT.

• Received 20 December 2002

DOI:https://doi.org/10.1103/PhysRevLett.91.216603