Browsing by Author "Yurtsever, A."

Now showing 1 - 5 of 5

Open Access
Dynamic correlation effects on the plasmon dispersion in a two-dimensional electron gas
(The American Physical Society, 2003) Yurtsever, A.; Moldoveanu, V.; Tanatar, Bilal
The charge-density oscillations (plasmons) of a low-density two-dimensional uniform electron gas are studied within the framework of finite temperature and frequency dependent (dynamic) version of Singwi, Tosi, Land, and Sjölander theory and compared with the recent experimental results. The use of the Hartree-Fock approximation for the static structure factor leads to a finite temperature dynamical counterpart of the static Hubbard approximation. We observe important differences between dynamic and static local-field factors as well as between the corresponding plasmon dispersion laws. Our calculated plasmon energies that include dynamic correlations are in very-good agreement with the recent experimental results.
Open Access
Ladder approximation in coupled quantum-well systems
(American Physical Society, 2001) Yurtsever, A.; Tanatar, Bilal
We study the contact values of the interlayer pair-correlation function in electron-electron and electron-hole double-layer systems. For this purpose the ladder approximation as generalized to multicomponent systems is used. The ladder approximation yields positive values for the interlayer gee(0) and geh(0) for all values of the density parameter rs and layer spacing d. This allows us to infer possible instabilities in the system more reliably compared to other approaches. We also investigate the effects of quantum-well width and screening on the interlayer pair-correlation functions.
Open Access
Many-body effects in the Coulomb drag between low density electron layers
(Elsevier Science, 2003) Yurtsever, A.; Moldoveanu, V.; Tanatar, Bilal
Recent Coulomb drag experiments in low-density double-layer electron systems have the power of distinguishing various many-body formulations of the effective interactions. In this work we theoretically study the correlation effects on the drag resistivity in these systems within various models. The effective inter-layer interactions are best described by the generalization to the double-layer case of the Kukkonen-Overhauser approach which differs significantly from the self-consistent field approach of Singwi et al. [Phys. Rev. 176 (1968) 589]. Following the formulation of Vignale and Singwi [Phys. Rev. B 32 (1985) 2156] we derive an expression for the effective inter-layer interaction which embodies the many-body correlations through the local-field corrections. The drag resistivity is calculated within this approach together with the Hubbard approximation for the intra-layer local-field factor and a simple model for the inter-layer correlations. Comparison with the recent measurements of Kellogg et al. [Solid State Commun. 123 (2002) 515] yields very good agreement. Our results are also contrasted with the corresponding drag resistivities given by the Singwi et al. theory, the dynamic random-phase approximation and the Hubbard approximation. The significant differences found between these theories emphasize the strong sensitivity of the drag resistivity to the effective inter-layer interactions.
Open Access
Model boson fluid with disorder in the self-consistent field approximation
(2001) Yurtsever, A.; Tanatar, Bilal
We study the ground-state properties of a model neutral boson fluid in the presence of disorder effects. The effective interaction between the bosons is obtained through the self-consistent field method which renormalizes the bare interaction consisting of a hard-core repulsive potential with an attractive tail at zero temperature. We introduce disorder effects within a number-conserving approximation by modifying the density - density response function. Our results for the static structure factor and the collective mode dispersion reflect the effect of disorder in qualitative agreement with other calculational approaches. © 2001 Elsevier Science B.V. All reserved.
Open Access
Short-range correlations in coupled quantum-wire systems
(TÜBİTAK, 2002) Yurtsever, A.; Tanatar, Bilal
We study the contact values of the inter-wire pair-correlation function in electron-electron and electron-hole double-wire systems. For this purpose the ladder approximation as generalized to multicomponent systems is used. The ladder approximation yields positive values for the inter-wire gee(0) and geh(0) for all values of the density parameter rs and distance d between the wires. This allows us to infer possible instabilities in the system more reliably compared to other approaches. We also investigate the effects of quantum-wire width and screening on the inter-wire pair-correlation functions.