J. Szymański

New approach to calculation of the sticking coefficient

Abstract Sticking coefficients calculated in the distorted wave Born approximation (DWBA) often become greater than 1. The quantum formulation of sticking and desorption within DWBA is re-examined to correctly account for the processes occurring on the time scale of the interaction time of extended states with the surface. It results in expressions for renormalized sticking coefficients properly bounded by 1. A modified master equation for physisorption kinetics containing renormalized transition rates between continuum and bound states is proposed.

Collective modes in the two-dimensional electron liquid near the Wigner phase transition

We have investigated the properties of the collective modes of the two dimensional electron liquid in regions of phase space near the Wigner phase transition. We used a new method which we have recently developed for dealing with the strongly correlated electron liquid. We find that the dynamical correlations cause the dispersion curve of the 2D plasmon to pass through a maximum, leading to negative dispersion for largerq values and a much reduced value for the plasmon cut-offqc. It was of interest to discover, on comparing the plasmon dispersion curve with the corresponding curve for the phonon in the Wigner crystal, that the negative dispersion of the plasmon duplicated the turnover of the phonon dispersion curve at the edge of the Brillouin zone,q=1.2G, and that the two curves were in close agreement for allq less than the plasmon cut-off. A new collective mode in the liquid phase on the highq side of the single-particle excitation spectrum was also found to match up with the phonon dispersion curve nearq∼G.

Exact Solution for the Hartree Fock Approximation to the Electron Gas

We report on the first exact numerical solution for the leading corrections to the RPA dynamic response function χ(q, ω) for the electron gas at metallic densities. The corrections comprise the exchange terms to the RPA together with the static Hartree-Fock self-energies. Results are presented for the dynamic Structure Factor S(q, ω) and we compare this with the previous approximate results. An unexpected shoulder is observed on the low energy side of the main peak of S(q, ω).

Dynamic Correlations in the Electron Gas: The Mean Field Picture and Beyond

A systematic examination of dynamic correlations within the metallic electron gas is given. The applicability and limitations of the Mean Field picture are critically discussed. Also mentioned are evidence of multi-pair excitations, and problems of separating in the experimental data genuine Many-Body effects from Crystalline effects. Finally, areas where important new Many-Body effects are likely to be in evidence are pointed out.

Multipair Excitations and Dynamic Response of the Metallic Electron Gas in Two and Three Dimensions

We demonstrate, using a quantitative microscopic formalism, that multipair excitations significantly affect the dynamic response of the electron gas even for densities as high as rs = 2 in the bulk. For the two-dimensional electron gas in GaAs/GaAlAs heterostructures we find that the effects of multipair excitations are even more pronounced, indicating that the standard single particle description of 2D electron systems should be used with caution. We discuss the essential role that multipair contributions at high frequency play in maintaining the frequency moment sum rules for the dynamic response of the electron gas.