Mixed-valence states at a crystal surface: SmS

We present a model calculation, based on the Falicov-Kimball model for metal-insulator transitions, which shows that for a mixed-valence solid with a surface, the average valence of the atoms at the surface may be substantially different from that in the bulk. The effect, which we have calculated only for T = 0 and neglecting hybridization, is due to the different local density of itinerant states at the surface and bulk atoms. Surface states contribute to the valence difference but are not solely responsible for it.     

Non-parabolicity and transverse mass of electron carriers in silicon

It is shown that band structure effects give a small but not negligible contribution to the transverse cyclotron mass enhancement in silicon [100] field effect transistor devices. For carrier concentrations of about 8 × 10¹² electrons per cm² the mass increases by approximately $\text{Δm}{}^1\text{= 0.005}$, i.e. 2.4%. In opposition to the many-body corrections, the band structure enhancement increases with concentration.     

A Cluster-Bethe-Lattice approach to spin-waves in dilute ferromagnets

We study the spin-wave spectra of a dilute ferromagnet within the cluster-Bethe-lattice approximation. Short range order effects for the alloy are included. A study of finite size clusters connected at their edges to Bethe lattices of the same coordination number allows us to determine: (i) the stability condition for the magnetic system; (ii) the continuum spin-wave local density of states; and (iii) the existence of localized states below and above the continuum states.