Dilute Electron Gas near the Metal-Insulator Transition: Role of Valleys in Silicon Inversion Layers

We emphasize the role of valleys in the transport properties of the dilute electron gas in Si-MOSFETs. Close to the critical region of the metal-insulator transition the decrease in the resistivity up to 5 times has been captured in the correct temperature interval by a renormalization group analysis of the interplay of interaction and disorder. No adjustable parameters are involved in the analysis if the electron band is assumed to have two distinct valleys. The considerable variance in the data obtained from Si-MOSFET samples of different quality is attributed to the sample-dependent scattering rate across the two valleys, while universal behavior is expected to hold when the intervalley scattering is negligible.