Theory of transport properties of the sixfold-degenerate two-dimensional electron gas at the H-Si(111) surface

We consider the mobility of the interacting two-dimensional electron gas as realized at the hydrogen terminated Si(111) surface with sixfold valley degeneracy. For zero temperature we calculate the mobility as function of the electron density for charged-impurity scattering. We take into account many-body effects. Multiple-scattering effects, leading to a metal-insulator transition at low electron density, are also taken into account. Our calculation is in agreement with recent experimental results. We also present analytical results for the mobility and we study the importance of interface-roughness scattering. For the spin-polarized electron gas, created by applying a parallel magnetic field, we predict the mobility and the phase diagram of the metal-insulator transition.