We have found that the conduction in Si-MOS structures has a substantial imaginary component in the metallic phase for the density range 6 \times n_c > n > n_c, where n_c is the critical density of the metal-insulator transition. For high mobility samples, the corresponding delay (or advance) time equals approximately to 0.1 - 10ms and increases exponentially as density and temperature decrease. In very low mobility samples, at temperature of 0.3K, the time-lag in establishing the equilibrium resistance reaches hundreds of seconds. The delay (advance) times are approximately 10^2-10^8 times larger than the overall RC-time of the gated structure. These results give evidence for a non-Boltzmann character of the transport in the low-density metallic phase. We relate the time-dependent effects to tunneling of carries between the 2D bulk and localized states.
@article{arxiv.cond-mat/9907401,
title = {Time-dependent Effects in the Metallic Phase in Si-MOS: Evidence for Non-Diffusive Transport},
author = {V. M. Pudalov and G. Brunthaler and A. Prinz and G. Bauer and B. I. Fouks},
journal= {arXiv preprint arXiv:cond-mat/9907401},
year = {2007}
}