Ground-state properties of double-wire semiconducting systems
Author
Mutluay Müstecaplıoğlu, Nihal
Advisor
Tanatar, Bilal
Date
1997Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
73
views
views
37
downloads
downloads
Abstract
With the recent advances in nanometer-scale semiconductor device fabrication
technology, it became experimentally possible to produce strongly confined
electron systems. Quantum wires are among these systems, and are attracting
increasing interest due to their potential applications in solid-state device
technology such as high-speed transistors, efficient photodetectors and lasers.
Quantum wires are quasi-one-dimensional systems where electrons are free
to move in one dimension, but their motion is restricted in the remaining
two dimensions. Various models for qucisi-one-dimensional structures have
been proposed in the literature, such as cylindrical, square-well and parabolic
confinements.
in this thesis, we examine ground-state correlations in double-quantum-wire
systems within the self-consistent scheme of Singwi et ai, namely the STLS
approximation. The model we adopt consists of two parallel cylindrically-confined
quantum wires. The cases when both wires have electrons as charge carriers and
when one wire has electrons while the other has holes are considered. Under
the assumption that only one subband is occupied in each quantum wire and there is no tunneling between them, we calculate the local-field factors and static
correlation functions. Ground-state energy and collective modes are discussed
within the RPA, Hubbard and STLS approximations in order to compare the
results. Charge-density-wave instabilities in these structures are examined at
small and finite q values. Our numerical results are given for systems where the
carrier densities and the radii of both wires are equal.
As the charge carrier density is lowered, we observe that the importance of
local field corrections increases so that the RPA or Hubbard approximations do
not give reliable results in this region. We find that the interwire correlations
become quite important for electron-hole systems. Taking into account the
exchange-correlation hole around electrons, STLS provides a much better
description to this many-body problem compared to the previous models.
Keywords
Quasi-one-dimensional electron gasdouble-quantum-wire
exchange-correlation
local-field correction
static structure factor
density response function
dielectric function
pair correlation function
ground state energy
collective modes
charge-density-wave instability
random phase approximation
Hubbard approximation
STLS approximation