Fate of the extended states in a vanishing magnetic field: the role of spins in strongly-interacting 2D electron systems

摘要

In non-interacting or weakly-interacting 2D electron systems, the energy ofthe extended states increases as the perpendicular magnetic field approacheszero: the extended states "float up" in energy, giving rise to an insulator.However, in those 2D systems where metallic conductivity has been recentlyobserved in zero magnetic field, the energy of the extended states remainsconstant or even decreases as B -> 0, thus allowing conduction in the limit ofzero temperature. Here we show that aligning the electrons' spins causes theextended states to once more "float up" in energy in the vanishingperpendicular magnetic field, as they do for non- or weakly-interactingelectrons. The difference between extended states that float up (an insulator)or remain finite (a metal) is thus tied to the existence of the spins.