Gateable suppression of spin relaxation in semiconductors

The decay of spin memory in a 2D electron gas is found to be suppressed clo se to the metal-insulator transition. By dynamically probing the device usi ng ultrafast spectroscopy, relaxation of optically excited electron spin is directly measured as a function of the carrier density. Motional narrowing favors spin preservation in the maximally scattered but nonlocalized elect ronic states. This implies that the spin-relaxation rate can be both tuned in situ and specifically engineered in appropriate device geometries.