A new metallic state in two dimensions

Abstract We report the discovery of a new and unexpected kind of metal in two dimensions (2D), which exists in the presence of scattering by local magnetic moments. The experiment was carried out on a 2D electron system in silicon, where the local magnetic moments have been induced by disorder and their number was varied using substrate bias ( V sub ). In the new metal, the conductivity decreases as σ ( n s , T )= σ ( n s , T =0)+ A ( n s ) T 2 ( n s – carrier density) to a non-zero value as temperature T →0. In three dimensions, this T 2 dependence is well known, and results from Kondo scattering by local magnetic moments. In 2D, however, the existence of a metal with d σ /d T >0 is very surprising. As the number of local moments is reduced, the range of temperatures [ T T m ( V sub )] where they dominate transport becomes smaller. For T > T m , we observe the usual 2D metallic behavior with d σ /d T