Singwi, Tosi, Land And Sjolander Research Articles

Quasi-one-dimensional polaron gas in a GaAs quantum wire

In this work we present a study of the plasmon–longitudinal-optical (LO) phonon collective excitation as a function of the quasi-one-dimensional wave vector for several electronic densities and thickness of the wires. We observed that the intra- and intersubband excitation collective energies are very sensitive to electronic density variation. This effect is more pronounced for the lower branch of the collective excitation energy and for narrower wires. Our calculations are performed using the Singwi, Tosi, Land and Sjolander (STLS) theory, at zero temperature, assuming a three-subband model, where only the first subband is occupied by electrons.

Liquid 4He at Zero Temperature and the STLS Scheme

Within the framework of the self-consistent scheme proposed by Singwi, Tosi, Land and Sjolander (STLS) for an interacting system we study the properties of superfluid liquid 4He. By employing the Aziz potential (HFD-B) as the interaction potential between helium atoms, we have calculated the static structure factor, the pair-correlation function, the elementary excitation spectrum and the effective two-body interaction as a function of wave-vector, for different densities. Our results show considerable improvement over the Ng–Singwi’s model potential of a hard core plus an attractive tail and are comparable with experimental data. We have compared our results with experimental data and with the results of some theoretical models. Agreement between our results and the experimental data for the static structure factor for the small k values is fairly good.

Correlations in the Layered Electron Gas

The self-consistent theory of Singwi, Tosi, Land and Sjolander (STLS), which accounts for exchange and short-range correlation effects through an effective potential depending on the structure factor, is generalized to the Visscher and Falicov model of the layered electron gas. The complete numerical solution of the STLS self-consistent equations provides information about intraplane and interplane correlations. The local-field correction is obtained and compared with expressions from previous works, where the strong interplane coupling between the electrons is neglected. The pair correlation function, the correlation energy and the plasmon dispersion are evaluated for some typical values of the coupling constant r s of the electron system and the distance between the layers. For comparison, the Hubbard approximation and the random-phase approximation are also considered.

Wave propagation in strongly coupled quasi-one-dimensional quantum plasma in a magnetic field

A cold electron gas fills the lowest Landau level for superstrong magnetic fields and very low densities. In such cases, in general, the potential energy of the particles is equal to or greater than their kinetic energy (strongly coupled plasmas), and a special approach is called for. The STLS (Singwi, Tosi, Land, and Sjolander) approximation scheme is used to study the dispersion and damping of the low-frequency modes, i.e., the whistler and the extraordinary modes for zero temperature. The lowest order dispersion for all modes in consideration are unaffected by correlations, but for undamped plasmas the correlation term is of the order /gamma/a/sup 2/c/sup /minus/2/. Further, /delta/(/omega//sup 2/) for the whistler mode becomes infinite at /gamma/ = 3; its behavior critically depends on the filling number /eta//sub Fc/ = /epsilon//sub F///Dirac h//Omega/, where /epsilon//sub F/ is the Fermi energy and /Omega/ is the electron cyclotron frequency.

Wave propagation in strongly coupled classical plasmas in an external magnetic field

When a small perturbation is applied to the plasma dispersion, a small shift of frequency due to correlation occurs. This is justified even for strong coupling, since the effect is proportional tok2 (k is the wave vector) and it is sufficient to consider thek → 0 limit. Then by solving the dispersion relations forδω, the shift of frequency due to correlation, at different angles of propagation, we obtain all information needed. The plasma modes in which we are primarily interested are the “whistler” and the “extraordinary” modes. In this work the STLS (Singwi, Tosi, Land, and Sjolander) approximation scheme is used. It is seen that the correlational effects enter only through terms of orderk6 for the whistler mode and terms of orderk2 for the nonresonant situation of the extraordinary mode.