Local moments near the metal-insulator transition

This paper examines in detail the phenomenological local-moment model Hamiltonian used recently by Paalanen, Graebner, Bhatt, and Sachdev [Phys. Rev. Lett. 61, 597 (1988)] to understand experiments on metallic phosphorus-doped silicon near the metal-insulator transition. The model describes the disordered metal in terms of two components: itinerant quasiparticles which lead to charge transport and electron local moments. Fermi-liquid properties of the itinerant quasiparticles in the presence of the low-energy spin fluctuations of the local moments are calculated. The local moments lead to strong spin-flip quasielastic scattering of the itinerant electrons; this scattering leads to a temperature dependence of the conductivity and modifies quantum-interference effects near the metal-insulator transition.