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. In particular, in both low- and high-disorder systems, the insulating state is a Coulomb glass. To address the fundamental question whether glassy behavior of electrons exists in the absence of long-range Coulomb interactions, we studied strongly disordered 2D electrons in thin-oxide Si devices in which the Coulomb interaction is screened by the nearby metallic gate. We measured the relaxations of conductivity after excitation out of equilibrium made by a large change of carrier density n_s, over a wide range of temperatures and n_s, spanning the 2D MIT. The results show differences in the dynamics compared to the case of long-range interactions, indicating the key role of long-range Coulomb interactions in the existence of glassy behavior of electrons near the 2D MIT in strongly disordered samples.