Onset of Glassy Dynamics in a Two-Dimensional Electron System in Silicon

The fluctuations of conductivity σ with time have been studied in a two-dimensional electron system in low-mobility Si inversion layers. The noise power spectrum is ~1/f^α with α exhibiting a sharp jump at an electron density nₛ0ex0ex=0ex0exng. A huge increase in the relative variance of σ is observed as nₛ is reduced below ng, reflecting a dramatic slowing down of the electron dynamics. This is attributed to the freezing of the electron glass. The data strongly suggest that glassy dynamics persists in the metallic phase.