Frequency-dependent conductivity of a strongly disordered two-dimensional electron gas

We compare the predictions of G\"otze's theory for the strongly disordered two-dimensional electron gas based on a self-consistent current-relaxation kernel with experimental temperature and frequency-dependent conductivities σ(T,ω) measured in n inversion layers on Si(100) surfaces. With a unique value for the strength and range of the random potential one can achieve a convincing fit to both σ(T,ω=0) and σ(T=0,ω) over a range of electron densities that span the "metal"-insulator transition. The satisfactory agreement is conditional on the assumption that the valley degeneracy is lifted.