Showing papers by "Fernando Flores published in 1995"

Quasi-one-dimensional structures and metallization for the deposition of K on GaAs(100) As-rich surfaces.

Abstract: A local-density linear combination of atomic orbitals method has been applied to study the depostion of a K overlayer on the As-rich GaAs(100)-2\ifmmode\times\else\texttimes\fi{}4 reconstruction. Our results show that the K atoms form quasi-one-dimensional structures along the missing rows of the semiconductor surface. The conduction band associated with the K orbitals is analyzed by means of an extended Hubbard Hamiltonian. We show that a Mott transition appears for a deposition of 6--7 K atoms per unit cell, and argue that for this coverage the metal-semiconductor barrier is almost completely formed.

Theory of circular dichroism in photon stm experiments on magnetic samples

Abstract: Recent experiments on the circular dichroism using a photon emission scanning tunneling microscope (PSTM) on magnetic samples are analyzed by a theoretical approach that includes the influence of the sample-tip geometry and the anisotropic response of the ferromagnetic substrate. We obtain an expression for the degree of circular polarization in the emitted light that leads to a reasonable agreement with the experimental data. Combining our theoretical analysis with measurements of the circular dichroism using PSTM offers a convenient way to determine locally the optical constants of a magnetic sample.

Nonlinear effects in interactions of swift ions with solids

Abstract: When a charged particle penetrates a solid, the response of the electrons is nonlinear in the charge of the projectile, except in the high-velocity limit. This response is of interest in connection with the wake of induced electron density and its various consequences, including energy loss of the particle. In this work, several theoretical approaches to the nonlinear wake of swift particles in an electron gas are compared. These include a hydrodynamical model, a many-body perturbation-theory formulation using a random-phase approximation, the time-dependent Hartree approximation, and two methods within time-dependent density functional theory.

Polarization interaction in relation to structure of liquid metals

Abstract: Following a short review of progress in understanding structure and forces in simple liquid metals such as Na and K, and in particular the role of the conduction electrons in mediating long-range oscillatory effective ion-ion interactions, attention is focused on polarization interactions. In such bulk liquid metals, oscillatory pair potentials o(R) of the long-range asymptotic form cos(2k F R)/R 3, where k F is the Fermi wavenumber, are shown to be corrected at large R by a polarization term falling off as R -4. The modifications brought about when the polarization interaction takes place in a heterogeneous environment such as that in a metal surface liquid or solid are discussed. The oscillatory interaction for a pair of ions parallel to such a planar metal surface is already known to be of shorter range than in bulk liquid metals, namely, cos (2k F R)/R 5. It is demonstrated here that for this same parallel configuration the polarization is also of short range, falling off as R -8. The case of arbitrar...