Phonon renormalization effects in low dimensional electron-hole systems
Author
Güven, Kaan
Advisor
Tanatar, Bilal
Date
1995Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Ia)vv (linuMisioiial sciniromluclor st i iid iii4's lia\4‘ 1и‘(М1 an (‘Xt(Misiv(‘ i4\soa,rrh iwcix
ill (4)iul(4iscd iiiatlcr physics. In j^aii iculai', iiindi (‘llorl has 1)(Ч'п dcvolnd to lhc‘
study ol ciuasi-one-diiiK'iisional siMniconductor sli-iiclures in гесчмП, yc'ars. The
IK'W physic'al pluMioiiK'iia. in\'ol\4*d in tlu'sc* sysitMUs arisin,^ diu‘ to th(‘ Г(‘(1п(чм1
dimensionality point to various |)ot(Milial applicalions for iuture teclinologi(.‘s.
y\ltliough the theory is lainiliar with tin* "oiK'-dimensionar’ pi’oblem for a long
time, the realization of such structures (also known as (juanlum wires) extends
onl}^ to ¿1 decade belonx Ilowciver, the по\ч'1 рго(1 исГкя1 t(‘chni([n('s led to a rapid
increase in the experimental studies which, in turn, required a mor(' realistic and
comi)rc*hensive theory to anal^'/c' and int('rpr('t tln^ obtaiiKnl data. This tlu'sis
work intends to make a contribution in i1k‘ diiH’ctioii of th(‘S(' imj>rovem(‘nts.
Our study is based on a (juasi-one-diiiKMisional eh'ctron-hole syst em as realized
in pliotoexcit(‘d quantum wires, interacting with tlu' bulk bO-])honons. VVe
investigate the polaronic corrections to the band gap and the c:arri(n* eilective
mass, cirid the dependence of this correction itself to carrier density, temperature,
and quantum finite size effects. VVe apply two different formal approaches; tho' p(n·Lurl.)гıtion theory and the vaiiational iiK'thod. 'I'he latter enables the
investigation of dynamical screening elfects, thereby clarifying tin? (luestion of
validity of the static screi'iiing approximation in one dimension. Our results have
shown that dynamical screening is r<'levant in low dimensions. The dielectric
function, which is a key quantity in describing tin' many-particle properties, is
analyzf'd under diihn(*nt tip'proximations such as the 1 lartree-Fock ap[)roximation,
random-|)hase api)roximation. and the more advaiuaxl local-field correction.
Several confinement |)otentials (inlinit(‘ well, paralrolic, cj lindrical) are presented.
I'kxplicit results iirc.' ol)tained hn' a (¡a.As (|uan(iim wiiv.
VVe compare the results of tin' |)olar(niic corn'cticnis with tluit of tin? (‘xchangecorndalion
induced corrections. W'e loiiinl that they are comi)arable in orrler
of magnitudi', indicating that cari'i('r-|)lu)non int('iactions are more enhanced as
the dimensionality reduces, and Ik.micc' should be treated on tin etpial footing
along with the carrier-carri(‘r interact i(jiis. WV* make comparison with the
pohironic corrections in two diiiK'iisiinial sysUnus. kdiially, we brielly discuss
the renormalization due to confined phuiions as well.
Keywords
Low dimensional electron gasexchange-correlation
electronphonon interaction
polarons
random-phase a])proximation
Ilartree-Fock approximation
dielectric function