The 2D metal-insulator transition as a strong localization induced crossover phenomenon

Low-disorder and high-mobility 2D electron (or hole) systems undergo an apparent metal-insulator-transition (MIT) at low temperatures as the carrier density (n) is varied. In some situations, the 2D MIT can be caused at a fixed low carrier density by changing an externally applied in-plane magnetic field parallel to the 2D layer. d\rho/dT changes its sign at some nonuniversal sample-dependent critical carrier density n_c separating an effective 2D metal (d\rho/dT >0) for n>n_c from an effective 2D insulator (d\rho/dT<0) for n