Out-of-equilibrium dynamics in a 2D electron system with screened Coulomb interactions

Considerable experimental evidence suggests that Coulomb interactions are responsible for a variety of phenomena observed in the metallic regime of 2D systems, as well as for glassy behavior near the 2D metal-insulator transition (MIT) and in the insulating regime. To address the fundamental question whether glassy behavior of electrons exists in the absence of long-range Coulomb interactions, we report a study of conductivity relaxations after excitation out of equilibrium, in particular after applying a large change of carrier density n_s, over a wide range of temperatures and n_s, spanning the 2D MIT. Experiments were performed on strongly disordered thin-oxide Si MOSFETs in which the Coulomb interaction is screened by the nearby metallic gate. The results show differences in the dynamics compared to the case of long-range interactions, and suggest the key role of long-range Coulomb interactions in the existence of glassy behavior of electrons near the 2D MIT in strongly disordered samples.