Evidence For Mixed Phases And Percolation At The Metal-Insulator Transition In Two Dimensions

The in-plane magnetoconductance of the strongly interacting two-dimensional electron system in a silicon MOSFET (metal-oxide-semiconductor-field-effect transistor) exhibits an unmistakable kink at a well-defined electron density, n(k). The kink at n(k) is near, but not at the critical density n(c) determined from resistivity measurements, and the density at which nk occurs varies with temperature. These features are inconsistent with expectations for a quantum phase transition. We suggest instead that this is a percolation transition and present a detailed model based on the formation of a mixed insulating and metallic phase within which a metal-insulator transition takes place by percolation.