Browsing by Author "Bennett, C. R."

Now showing 1 - 8 of 8

Open Access
Band-gap renormalization in quantum wire systems: dynamical correlations and multi-subband effects
(Institute of Physics Publishing, 2000) Güven, K.; Tanatar, Bilal; Bennett, C. R.
We study the band-gap renormalization m a model semiconductor quantum wire due to the exchange-correlation effects among the charge carriers. We construct a two-subband model for the quantum wire, and employ the GW-approximation to obtain the renormalized quasi-particle energies at the optical band edge. The renormalization is calculated as a function of electron-hole plasma density and the wire radius. Our results show that the very presence of the second subband affects the renormalization process even in the absence of occupation by the carriers. We compare the fully dynamical random-phase approximation results to the quasi-static case in order to emphasize the dynamical correlation effects. Effects of electron-phonon interaction within the two-subband model are also considered.
Open Access
Confined optical phonon effects on the band gap renormalization in quantum wire structures
(Elsevier Science, 1999) Bennett, C. R.; Güven, K.; Tanatar, Bilal
We consider the different approximations for the bandgap renormalization (BGR) within the random phase approximation (RPA), the quasi-static limit and the plasmon-pole approximation, and compare with the full result. We then include bulk optical phonons and also the phonon confinement using the phonons from the dielectric continuum (DC) model. We show that the results are very similar except at low densities where the quasi-static results overestimate the renormalization.
Open Access
Confined-phonon effects in the band-gap renormalization of semiconductor quantum wires
(American Physical Society, 1998) Bennett, C. R.; Güven, K.; Tanatar, Bilal
We calculate the band-gap renormalization in quasi-one-dimensional semiconductor quantum wires including carrier-carrier and carrier-phonon interactions. We use the quasistatic approximation to obtain the self-energies at the band edge that define the band-gap renormalization. The random-phase approximation at finite temperature is employed to describe the screening effects. We find that confined LO-phonon modes through their interaction with the electrons and holes modify the band gap significantly and produce a larger value than the static ∈0 approximation.
Open Access
Dynamical screening effects in a coupled quasi-one-dimensional electron-phonon system
(Institute of Physics Publishing Ltd., 1995) Bennett, C. R.; Constantinou, N. C.; Tanatar, Bilal
A fully dynamical and finite-lempel'dture study of the electron momenhum relaxation rate and mean free path in a coupled system of electrons and bulk LO phonons in a quantum wire structure is presented. Electmn-electron and electron-phonon interactions are eeated on an &at footing within the leading-order perturbation theoq and random-phase approximation. It is demonstrated that coupled-mode effects drastically change the tramport propties of the system at low temperatures. In panicular. the 'plasmon-like' and 'LO-phonon-like' excitations yield comparable rates which, as a consequence of the singular nahlre of the ID density of states, can be large at the threshold. This is in contrast to room temperature results where oniy the LO-phonon mode conuibutes significantly to the rate.
Open Access
Dynamical screening effects in hot-electron scattering from electron-hole plasma and LO-phonon modes in quantum wires
(Elsevier, 1996) Bennett, C. R.; Tanatar, Bilal; Constantinou, N. C.
We present a fully dynamical and finite temperature study of the hot-electron momentum relaxation rate and the power loss in a coupled system of electron-hole plasma and bulk LO-phonons in a quantum wire structure. Interactions of the scattered electron with neutral plasma components and phonons are treated on an equal footing within the random-phase approximation. Coupled mode effects substantially change the transport properties of the system at low temperatures. Particularly, the "plasmon-like" and "LO-phonon-like" excitations yield comparable rates which, as a consequence of the singular nature of the ID density of states, can be large at the threshold. This is in contrast to room temperature results where only the LO-phonon mode contributes significantly to the rate. The density and temperature dependence of the power loss reveals that dynamical screening effects are important, and energy-momentum conservation cannot be satisfied above a certain density for a given initial energy.
Open Access
Effect of cross-sectional geometry on the RPA plasmons of quantum wires
(Pergamon Press, 1994) Bennett, C. R.; Tanatar, Bilal; Constantinou, N. C.; Babiker, M.
The effect of cross-sectional geometry on both the intrasubband plasmon and intersubband plasmon of a quantum wire is investigated within a two-subband RPA scheme. Exact analytical electronic wavefunctions for circular, elliptical and rectangular wires are employed within the infinite barrier approximation. It is found that for fixed cross-sectional area and linear electron concentration, the intrasubband plasmon energy is only marginally dependent on the wire geometry whereas the intersubband plasmon energy may change considerably due to its dependence on the electronic subband energy difference. © 1994.
Open Access
Energy relaxation via confined and interface phonons in quantum-wire systems
(American Physical Society, 1997) Bennett, C. R.; Tanatar, Bilal
We present a fully dynamical and finite temperature study of the hot-electron momentum relaxation rate and the power loss in a coupled system of electrons and confined and interface phonons in a quantum-wire structure. Renormalization effects due to electron-phonon interactions lead to an enhancement in the power loss similar to the bulk phonon case.
Open Access
Screening effects on the confined and interface polarons in cylindrical quantum wires
(American Physical Society, 1996) Tanatar, Bilal; Güven, K.; Bennett, C. R.; Constantinou, N. C.
We study the contribution of confined and interface phonons to the polaron energy in quantum-well wires. We use a dispersionless, macroscopic continuum model to describe the phonon confinement in quantum wires of circular cross section. Surface phonon modes of a free-standing wire and interface phonon modes of a wire embedded in a dielectric material are also considered. Polaron energy is calculated by variationally incorporating the dynamic screening effects. We find that the confined and interface phonon contribution to the polaron energy is comparable to that of bulk phonons in the density range N=105-107 cm-1. Screening effects within the random-phase approximation significantly reduce the electron-confined phonon interaction, whereas the exchange-correlation contribution tends to oppose this trend at lower densities.