Quenched disorder effects in electron transport in Si inversion layers in the dilute regime

Abstract

In order to reveal the effects of disorder in the vicinity of the apparent metal-insulator transition in 2D, we studied electron transport in the same Si device after cooling it down to 4 K at different fixed values of the gate voltage Vcool. Different Vcool did not significantly modify either the momentum relaxation rate or the strength of electron-electron interactions. However, temperature dependences of the resistance and the magnetoresistance in parallel magnetic fields in the vicinity of the 2D metal-insulator transition carry a strong imprint of the quenched disorder determined by Vcool. This demonstrates that the observed transition between the metallic and insulating regimes, besides the universal effects of electron-electron interaction, depends on the sample-specific localized states (disorder). We report on evidence for a weak exchange of electrons between the reservoirs of extended and resonant localized states that occur at low densities. The strong cool-down dependent variations of ρ(T), we believe, are evidence for a developing spatially inhomogeneous state in the critical regime.