Interaction effects in conductivity of a two-valley electron system in high-mobility Si inversion layers

We have measured the conductivity of high-mobility (001) Si metal-oxide-semiconductor field effect transistors over wide ranges of electron densities n=(1.8-15)x10(11) cm(-2), temperatures T=30 mK-4.2 K, and in-plane magnetic fields B-parallel to=0-5 T. The experimental data have been analyzed using the theory of interaction effects in the conductivity sigma of disordered two-dimensional (2D) systems. The parameters essential for comparison with the theory, such as the intervalley scattering time and valley splitting, have been measured or evaluated in independent experiments. The observed behavior of sigma, including its quasilinear increase with decreasing T down to similar to 0.4 K and its downturn at lower temperatures, is in agreement with the theory. The values of the Fermi-liquid parameter obtained from the comparison agree with the corresponding values extracted from the analysis of Shubnikov-de Haas oscillations based on the theory of magneto-oscillations in interacting 2D systems.