Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers

The temperature and density dependence of the phase coherence time $\tau_\phi$ in high-mobility silicon inversion layers was determined from the magnetoresistivity due to weak localization. The upper temperature limit for single-electron quantum interference effects was delineated by comparing $\tau_\phi$ with the momentum relaxation time $\tau$. A comparison between the density dependence of the borders for quantum interference effects and the strong resistivity drop reveals that theses effects are not related to each other. As the strong resistivity drop occurs in the Drude regime, the apparent metallic behavior can not be caused by quantum coherent effects.