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 $n = (1.8-15)\times 10^{11}$\,cm$^{-2}$, temperatures $T = 30$\,mK$-4.2$\,K, and in-plane magnetic fields $B_\parallel= 0-5$\,T [1]. The experimental data have been analyzed using the theory of interaction effects [2] 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 [1,3]. The observed behavior of $\sigma$, including its quasi-linear increase with decreasing $T$ down to $\sim 0.4$\,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 [4]. [1] N.\,N.\,Klimov {\em et. al.}, PRB {\bf 78}, 195308 (2008). [2] G.\,Zala {\em et. al.}, PRB {\bf 64}, 214204 (2001); {\bf 65}, 020201(R) (2001). [3] A.\,Yu.\,Kuntsevich {\em et. al.}, PRB {\bf 75}, 195330 (2007). [4] Y.\,Adamov {\em et. al.}, PRB {\bf 73}, 045426 (2006).