Sharply increasing effective mass near the 2D metal–insulator transition

We report measurements of the effective mass and Landé g factor in strongly interacting two-dimensional systems in silicon. A sharp increase of the effective mass has been observed near the metal–insulator transition, while the g factor remained nearly constant and close to its value in bulk silicon. Furthermore, the enhanced effective mass has been found to be independent of the degree of spin polarization, which points to a spin-independent origin of the mass enhancement, in contradiction with existing theories.