80 GIAO DUC vA DAo TAO
D~ HQCQuacGIA TP. HCM
TRuONG D~I HQC KHOA HQC Tt!NHIEN
CAO BUY THll;N
, ,.:' A'" 7 ,.:'
TINH CHAT D~N VA QUANG CUA T~p CHATVA
A K 7
EXCITON TRaNG DAY GIENG LUQNG TV
A" "', A' ,
Chuyen nganh: V~T LY LY THUYET VA V~T LY TOAN
Ma 56 : 1.02.01
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TOM TAT LUhN AN TIEN SI V~T LY
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THANH rHO HO CHI MINH -1999
Lu~n an duqc ho~mthanh t~i ~ mOll V~t 19L9 thuy€t, Khoa V~t 19,Truemg
D~i hQc Khoa hQc 1\r nhien, D~i hQc Qu6c gia TP H6 Chi Minh va Phong
V~t 19L9 thuy€t, Phan vi~n V~t 19TP H6 Chi Minh, Trung tam Khoa hQCva
C6ng ngh~ Qu6c gia.
Ngll'Oi hl16'ng dfin khoa hQc : 1. GSTS

ddi dang ke so vcricac v~t li~u ban dAftkh6i. M()t trong cac vi cllu trUc nay la cac
h~ dfiy gi~ng luqng tU(quantum-well wire (QWW». Trong cac h~ nay, cac h~t till bi
giam nMt trong 2 chieu khOng gian, sl! chuyen dQng tinh ti~n theo lr\Ic dfiy thAng
g6c vcrimiJtphAng giam nh6t Iii tl! do.
SI! thanh cOng trong vi~c cM t~o ra cac QWW dii cho phep ngueri ta sir d\mg
chung trong cac d\mg c\l ban dAn, d6ng thCriqUail sat duqc nhieu hi~n tUqng ky I~
obu Hnh cMt phi tuy~n quang hQc, vi v~y, t~o nen mOt sl! qUail tfim dang ke trong
vi~c nghien CUllIy thuy~t cfing nhu thl!c nghi~m ve cac tmh cMt di~n va quang hQc
cua chUng.
Trong lanh VlJcly thuy~t, cac c6ng trinh nghien CUlltrucrc dfiy thuCrngsir d\lng
mOhinh rao thtgiam nh6t vOh~ hoiJc hiiu h~n c6 tfnh d6i XU-figcao nhu QWW tr\l,
QWW chli nh~t vcrirao th~ vOh~n. D6i vcricac QWW rao tht hiiu h~ c6 Hnh bIll
d6i xU"ngnhu QWW cM nh~t, QWW be m~t , kh6 khan cClban mang Hnh chIll Iy
thuytt la vi~c giro phuClngtrlnh SchrOdinger 2 chieu de dc djnh tr~g thai Dangluqng
cua h1;lttai. De khiic ph\lc kh6 khan nay, chUng tOisir d\lng g!in dung TlJa-Hartree dii
dltqc Bastard va Marzin dua ra gan dlly k€t hqp vcriphlfClngphilp bitn thj~n de xac
dinh tr1;lngthai Dang htqng cua h~ t1;lPcMt. Ben c~h do, anh hubng cua di~n truerng
ngoai left t~p chIll va exciton cfing duqc chung tOi xem xet bi'rivi tr~g thai di~n cua
h~ thuerng duqc thiim do bang vi~c sir d\lng mOt tfUerngngoai.
Ducri ki'ch thi'ch laser m~nh trong cac
Mban dAfthinh thanh plasma di~n tir-lei
tr6ng d~l.mdiJ.c,khi do do cac hi~u U"ngtlfClngquan-trao ddi va SI!cMn clla tuClnglac
Coulomb, nhieu tinh cMt dClnh~t clla h~ bi Mi chunn h6a nhlf khe dai se bi co I~i
ducri lac dOng clla cac hi~u U"ngnay va vi v~y clAnMn hi~u U"ngphi tuytn quang hQc.
Trong cac h~ ban clAnc6 CI!Cnhu GaAs sl! lien ktt gilia plasmon di~n tU-leitr6ng va
phonon quang hQc dQc (phonon La) cling la mOt hi~u U"ngdang qUail tfim. D6i vcri
QWW, cac. hi~u U"ngnay dii duqc qUail tfim nghien CUlltrong m()t vai flam rIll gall
1
dRy, IllYnhien trong cac cOng trlnh nay, ngum ta thuoog sit d\mg cac glin dung khac
nhall nhu gdn dung tinh, glin dung €o-giAtinh. Ngoai fa, nhu dii bi~t m<)tdiJc tr\1ng

nang lu<JI1grieng, ham m~t d<)phISva dO t<iichuAn bOa khe dill. Trong chu<1JJ.g4,
ding vm hlnh tMc lu~ ham Green Matsubara, chUng t6i da u6'c lu<JI1gduqc dO t<ii
chuAn bOa dill con du6'i t<icdOng cua hi~u li'ngchAodOng hQc nhieu dlli con v6'icac
glin dung thfch hqp.
BOi VIcac phu<1JJ.gpMp chUng t6i su d1.lng trong lu~n an la nhUng phu<1JJ.gpMp
quen thuOc cho cac mAll ban dAn kh6i. Do v~y, chUng t6i se kh6ng dua vao lu~n an
mOt chu<1JJ.gve phlin tOng qUaD ma chi diem qua mOt vai hi~n tU<JI1gco ban trong cac
Call trUc kh6i va Call trUc thap chieu trong ma dllu cua lu~n an fibula mOt phlin tOng
qUaD de thll'y ro h<1JJ.ve ,stf khac bi~t trong cac hi~n t\1<JI1gv~t 19 cua cac mAll ban dAn
kh6i va cac cliu trUc h~ thap chieu.
CHWNG I :HI~U UNGDI~ TRllNG TRENDAY GI~NG Ut;jNG Hi
Trong v~t 19 ban dan va di;i.cbi~t trong cac cliu trUc.ban dan gill mOt chieu stf co
m~t cua t/,\pcMt ion bOa the hi~n mOtvai tro qUaDtrQng trong co cM tlii a nhi~t d()
iMp cling nhu tl;\Ora m()t stf dich chuyen ml,lnhtrong phISquang hQc. Osorio, Degani
va Hipolito dii tfnh nang lu<JI1glien k~t cua t/,\pchlft trong day cM nh~t vui tfnh cMt
blft dang hu6'ng cua rao tM hihl hl,\D.Thy nhien, rao th! nay kh6ng cho phep chUng
ta tach bi!n trong vi~c gilli phu<1JJ.gtrmh SchrOdinger de xac djnh trl,\Dgthai Dang
lu<JI1gcua di~n tu. Glin day h<1JJ.,bai toan tI,lpcMt trong QWW du6'i tlic d()ng cua
di~n trI1emgding duqc qUaDtam nghien cUu.Narayani va Sukuma da nghien cUu bai
loan v&i stf co ml.\tcua t/,\pcMt lo/,\ihydrogen trong QWW cM nh~t rao tM vO hl,\D
d~t trong di~n truemg dell thang goc v6'i tT1.JcQWW.
Trong chu<1JJ.gnay, chUng t6i su d1.lngphu<1JJ.gpMp Ttfa-Hartree de xem xct Ilnh
huang cua di~n trI1emgtren cac day lu<JI1gtUbe ml.\tva dlly lu<JI1gtUchii nh~t rao tM
hihl h/,\n.
1.PhU<1JJ.gphap Tl!a-Hartree
3
Xua't phat ta phuo'l1gtrlnh SchrOdinger cho dAygieng luQ'l1gfir vcritM giam nh6t
V(x, y) :
{
n2

n2\J2
H = + V(x,y) + eF(y - Yo),
2m.
(6)
vcri Yo =< Y >F=O la gia tr, trung binh eua y trong tr~\IIgthai kMng co di~n trui'mg.
f-Him song thir eua tr~ng thai co ban va tr~ng thai kfch thfch dati lien :
w,,(x,y) = Nnwno(x,y)<P,,(x,y),n = 1,2
(7)
4
Wno(x,y) dugc lay nhu tfch cac nghi~m cua cac phuO'l1gtrinh T1,1a-Hartreecho Mi
Bastard va Mazin. Ham song bie'n thien q)n(x, y) :
q)n(X,y) = exp[-t1n(Y - Yo)], (8)
Chung t6i thtJc hi~n pMp Hnh bie'n thien d6i v6'i t1n de xac djnh cac muc nang
lugng cua di~n tit. Khi do, h~ s6 phAn ctJc cua di~n tit dugc dinh nghia nhu sau :
e
<1p = -F {(wdylwl)F;lo- (wdylwl)F=O}.
(9)
cac Hnhloan s6 dugc thtJchi~n cho dAyhrgng tit be m<}tGa(ln)As - GaAs
v6'icac tham s6 dii dugc sit d\mg : m* = 0.06mo, Lv = 50 A, VI = 0.15eV va
.6.V = 0.8eV.
Nang lugng tr~g thai c<1ban va kfch thfch thu nhat El va E2 nhu la ham cua
cuang dO di~n twang dugc bieu hi~n trong hinh 1. G6c tfnh nang lugng fJdAydugc
chQn la Dang lugng tr~g thai C<1ban cua QW c6 l~p va bang 69.1meV. Theo ke't
qua ma chUng t6i thu dugc thi cac muc nang lugng cua di~n tit giant khi cuang dO
di~n twang tang. Trong hlnh 2, chUng t6i ve d6 thj h~ s6 phAn clfc <1ptheo Lx. <1p
tang nhy khi Lx tang. Ngoai ra de so sanh, chUng t6i cfing xem xet twang hgp di~n
twang hu6'ng theo phuO'l1gcua trl}c x. Nhu co the thay tru6'c, chung t6i dii thu dugc
<1ptrong twang hgp nay phI}thu<)cml;lnhvao stJ thay dOi cua Lx.
3. T~p eMt trong dAy gieng luQ"ngtir du6i hie dOng eua di~n trub'ng
Trong khu6n kh6 cua g!in dung kh6i lugng hi~u dl}ng, Hamiltonian cua mOtdi~n

] }
- 2m" 8y2 + Vo Pl,xB(y2 - "4) + P2,x Bey) =E"g(y),
Eo = Ex+ E" - VO[P2,x+ P1,xP,,] ,
(14)
(15)
P" =
J
b2
B(y2 - "4)g2(y)dy,
J
a2
B(""4- x2)f2(x) dx,
J
a2
B(X2 - ""4)f2(X) dx.
(16)
P1,x =
P2,x =
Neu d~\tPI,x := 1 va P2,x := P" := 0, chUng ta se nMn dl1qe nghi~m dii dl1qe su dl;mg
bt'1i Osorio nhl1 dii n6i t'1tren. Ham thlt 4J(x,y, z) dl1qe eho dl1ai d;.tng:
4J(x, 1('z) = exp[-'x1f - rolJexp[-,B(xcosB + ysinB)] ,
(17)
Nang Il1qnglien k~t t;.tpeMt Eb :
Eb = E(,B,'x = O)min- E(,B,'x)min.
(18)
H~ s6 pMn Qre eua t;.tpeMt dl1qedinh nghia :
a" = - ~ {(iIllxcosB+ysinBIW)Ji'ofO - (iIllxcosB+ ysinBliII)F=O}.
F
(19)
Cae k€t qua bfuIg s6 th1!ehi~n eho QWW GaAs : Vo = O.4eV, m" = O.067mo

1. Giai thi~u
7
Ngltai ta dii chtffig to ph6 Mp tho va ph6 phat quang cM yeu gAyMi hi~u tffig
exciLon. Hau h~1cac nghien CUll1:9thuyet trltac dAyve QW cling nhu cac QWW sir
lh.HlgmO h111hrao Lhechii nh~t. Brum va Bastard dii nghien cuu hi~u tffigdi~n twang
I~n nung lulJng lien kef cua tr~ng thai CC1ban cua mQt exciton trong mQt QW. Brown
va Spector dii.tlnh nang luqng lien kef tr~g thai CC1ban cua mQtexciton bi giam nMt
LrongmQLQWW hlnh tf\! rao the vf:Jh~ va hlIu h~.
Glin dlly, Clk QWW rao tM bell parabol dii dltC;tcnhieu nha 1:9thuyet va thlfc
nghi~m nghien CUllMi vi mO h1nh nay dii mf:Jta t6t han cac kef qua tht!c nghi~m.
Trung chuang nay, chUng tf:Jise trlnh bay cac ketqua Hnh loan cua chUng tOive nang
luqng lien kef tr~ng thai CC1ban cua mQt exciton Wannier trong mQt QWW rao tM
bell parabol d~t trong di~n trltCrngngoai thAng goc vui tf\Ic QWW.
Vui Sl!hi~u biet ve exciton va cac ham song lien t\Jc va cac tri rieng nang Iuqng,
chung la co lh~ giai phuang trlnh phfin cl!c c~p di~Iitir-IOtr6ng d~ nh~ du<;1cdQphfin
qrc gHi'ncac d{1iva VIv~y co the Hnh du<;1Cph6 quang hQc cua cMt ban dan trong
vllllg mep duj. D~ dan Mn phuang trlnh pMn clfc c~p di~n tir-IOtr6ng, chung ta co
Lhesir d\lI1gcach tiep c~ ti':tphuC1ngpMp twCrngit! hqp ho~c tier c~n ti':tphuang phap
hum Green.
Trong Ln1lmghqp gall dung ban clan 2 vimg, bo qua st! chin va xct h~ trong dieu
ki~n ghi ca.nbhng, ta co dQcarn quang hQcc~p di~n tU- 10tr6ng trong gan dung RPA:
X(w) = -2ldcvl2 ~IY!/(r=oW [n(w+ i8)~ Eg - E/
1
]
20)
- n(w + i8) + Eg + E/' (
Lrongdo dcv la y~u t6 ma tr~n luO'ngcl!c. Y!/(f) la ham song tr~g thai c~p di~n tU-IO
trOng, E/ wang tffig la tri rieng nang luqng (ila t~p cac s6 Iuqng fir) va chung thoa
pl1l1l1ngtrlnh Wannier :
[

kh6i hrqng hi~u d\lng cua di~n tir va 10tr6ng. no. la be TOngcua khOng gian dai con
toan phau (0.
= We + w,,), voi fiuJeva fiuJ" tuang t1'ngla be TOngdai con cua di~n tir
va 10tr6ng trong the giam nh6t parabol. Tn;mg khuOn khO cua gau dung kh6i hrqng
hi~u d\lng, Hamiltonian cua h~ cho bcri
11,'1.82 r,,2 82 n2 82 mew~ 2 m"w~ 2
- 2me 8y~ - 2m" 8y~ - 2f L8Z2 + ~Ye + ~y"
e2
+eF(Ye - y,,)- I- -,.
Ere - rh
H =
(24)
Ham song thii trlplg thai C(Jban cua exciton:
\l!(r-;,r-;') = N (P(Ye)1>(y,,)exp{-Alr-; - 1'7,I} ,
(25)
9
b day tjJ(Ye)va tjJ(y,,)la ham song cuadi~n tit va 10tr6ng d<1nIe trong di~n tr\1ang.
Nang l\1qngIi~n ke'ttr:;mgthai co ban cuaexciton:
Eb = Eo - (wIHlw}min
,
(26)
trong do Eo la tOngHang l\1qngtr~mgthai co ban cua di~n tir va 16tr6ng d<1nIe trong
di~n twang.
Chung ta nh~ d\1C;1CHang Iuqng trl;lngthai co ban cua
exciton trong di~n twang
bilng cach qrc lieu theo ). tr, trung blnh cua nang Iuqng b trl;lng thai thir w.
3. Cae kef qua bang 86
Cac tfnh loan b5.ngs6 thvc hi~n cho QWW GaAs, vm cac tham s6 dii duqc sir
d~ng : me = O.O67mo,mh = O.45mova €= 12.53.
Nang luqng lien ke't Eb nhu la ham cua cuang d<)di~n tr\1ang duqc the hi~n trong

hQ dii daub gill qua caD d6ng gop cua phonon trong BOR.
Dl!u trell h11lhthuc
lulplham Green Matsubara,trong chuang nay chung tOise
xem xci phOniing Illqng rieng di~n tit, ham m~t dOpM, dOtai chua.n h6a khe dui va
chi h~nch~ iJd6nggop cuadill con tr~ng thai C<1ban trong ph~ vi g1indung PPA
bao g6m cu hi~u U"ngtUang lac h~t tai-phonon.
1. Hamiltonian cua h~ di~n tit-IO trong trong dAy gi€ng luqng tit
Toan tit Hamiltonian cho h~ di~n tUbi giam nh6t trong m~t phAng (x, y) cho biJi
Bcnllcr:
H = Ho +Hc. (27)
(28)
:Ho= ~ at n>,ak,n,>,Ek,n,>,, \= c,v
L J "
k,n,>'
tmng do, niing luqng cua di~n fir trong dui con thu n thuOc
daidan( \=c) :
1i,2k2
Ek,n,c = Eg + En,e + _
2
= Eg + Ce,n,k ,
me
(29)
Ilung Illqng cua 16tr6ng trong dill con thu n thul)c dillh6a trj ( \=v) :
Ti,2k2
E
k n v = -E n v - - = -c" n k
.
, , '2m" ' ,
(30)
11

115(q,ivrn) = Eoo+ n~,(ivtn) + n~l(q, ivrn) - E(q,ivrn) ,
(34)
trong d6 iv", lit tftn s6 Matsubara cho boson. Ham phall clfc m~g duge eho bbi :
EO- Eoo
nO (UJ)= W2'
L 1-;;;r.
(35)
Trong gall dllng PPA ham pIlau clfe di~n :
2
UJpl
n°
(q
UJ) = Eoo 2 - UJ2: zj2 '
el , UJq pi
(36)
2 nq2
UJpl= -V(q),
II
(37)
12
2 2
{
1
}
q4
CJJq = CJJpl 1+ V(q)I>- On. + 4p2'
,-e,h 7fiii
vUin Him~tdOdai plasrna.Khi do, ham di~nm6i :
(38)
2

g(CJJ)= ell:-l la ham pMn b6 boson
Ham m~tdOph6 dun h1;lt:
A.(k ) = 2Iml~i(k,CJJ)1
"CJJ (CJJ+ Pi - ei(k) - Re~i(k,CJJW+ [Im~i(k,CJJW .
(44)
13
Xet truCmghqp cua QWW GaAs v6i cac tham s6 dUc;1csir dl;mg: m. = O.O67mo,
mh = O.45mo, EO= 13.1, Eoo= 11.1, UJL= 36meV va n = lOR.
Trong hlnh 9, chUng tOichi ra phlin thl!c cua nang lu<JI1grieng 1:. (O,UJ)ciia di~n
tir. De so sanh, chung tOi ding trlnh bay cac ket qua cua glin dung EO.Ngoai 2 c()ng
hubng quell thu()c cua plasmon, chUng tOi nh~ duc;1cthem 2 c()ng hubng trong Ian
cQ.n:!:UJr,- It. khi tlnh den sl!ph1,lthu()c tlin s6 ciia ham phan cl!c m!p1g.
Ham mQ.td() phd cua di~n tit duc;1ccho trong hlnh 10. Cho tfUang hqp kMng co
dong gop cua phonon chung ta co 2 cl!c quen thu()c dii dUc;1cnghien cUu trong cac
mati 3-chieu, 2-chieu ding nhu l-chieu. Neu dem theo cpieu tang cua UJtit am den
duO'l1gchung ta co Cl!cdliu lien It s!\c net, dUc;1cgQi Iiiplasmaron. a,c thu 2 rllt s!\c
net dUc;1cgQi Iii.m()t gia h~t, Iii m()t kfch thlch rllt ro rang cua h~. Trong trtrang hqp
xem xet them lien ket phonon ta nhQ.n them dUc;1c2 cl!c t:;1ivi trl :!:UJL- M. ttrO'l1g
t\! nhu ph6 cua nang lu<JI1grieng, chi CI!Ccrvi trf -UJL - It. Iii.s!\c net, con ClfCa
+UJr, - It. chi co the thlly ro hO'l1crnhi~t d() caD.Ngoai ra khi nhi~t d() tang lien ket
phonon lam cl!cghi h~t giam d() snc net.
4. Ht) tai chu:\n h6a khe dai
Cho UJ-t ei(k) - Mi trong (46) ta thu dUc;1cbieu thuc cho nang lu<JI1grieng dO'l1
h:;1t:
1:.(k e.(k» = 1:~"'(k)- "
/
00 rid ImVs(q,UJ' + i8)[l + g(UJ/)- fi(k - q)]
, , , , ~ -00 7T ei(k) - ei(k - q) - UJI+ i8 .
q
. (45)

m~t d() phOcua di~n tit va dii tlm thAym()t dang di~u quell thu()c nhu trui'1nghQ'pv~t
li~u kh6i va QW. Chung t6i dii chUng to rAng gful dung £0 gia tinh chi th~t Sl!lam
vi~c t6t n€u th~ giam OO6t000 va nhu v~y gful dung nay co the t6t trong cae v~t li~u
kh6i. Ngoili ra chung t6i cling chUng to duQ'cgful dung £0 d()ng hQc lam vi~c rIftt6t
trong trui'1nghQ'pQWW. VI v~y chung t6i se sit d\lng gful dung nay trong chuo'ng 4.
CHWNG 4 : HI~U UNGCHANDONGHQC.MO HlNH NHIEUDAI CON
Trong cac QWW, do hi~u tffig giam OO6thlOOthanh cac dai con nang Iugng trong
15
dlii dfin cling nl1l1dlii hmi trioDo Sl!tach giG'acae dMcon thl1C1ng1611trong cac QWW,
VIv~y chung ta thl1C1ngxem xct m6 hlnh chi m<)tdlli con. Thy nhien, trong cac dieu
ki~n thl!c nghj~m nhl1b nhi~t d<)cao, SI!kfch thfch laser m~h, nhieu dill con bi chi€m
gill. 51!phfin b6 cac h!;}tt!\i tren cac dM con khllc nhau phill d6ng m<)tvai tro quaIl
trQng trong d<)tai chuAn h6a cae dMcon nhu dii duqc tlm tMy trong QW. Trong Wc
nhieu lac gill nghien cuu BGR cho m<)tdlii, Benner va Grcus dIng cac c<)ngsl! diitfnh
BGR cho nhieu dlli nhung chi trong gan dung Hartree-Fock, bO qua hi~u U'ngchiin
cua tvoog ruc Coulomb.
1. Cae yell t6 ma tr~n di~n m6i
Cling xuat pIlat tit m<')h'inh QWW rao th€ Mn parabol, y€u t6 ma tr~ cua tUO11g
ruc CoulombtraIl giiiacac h!;}ttIliduqc cho Mi trungb'inhtren cac ham rieng ~I(X)
cua the giam nh6t :
V(q)lmn = 2(;:2
/dx /dxl~i(x)~;(XI)~s(X')~m(x)KO(lq(x - Xl}!).
(47)
1M' chan cua tl1O11gruc Coulomb dl1qc cho trong ph!;\ffivi gan dung RPA nha
phl1O11gtrlnh Dyson:
~~srn(q,UJ)= ~rsm(q) + L ~r's'm(q)P::s,(q,UJ)Vs~rsr,(q,UJ),
r',s'
(48)
trong do P:~(q,UJ) la phan thl!c cua ham Lindhard l-chieu :
f rj rj

flr8m(q,W) = 1- 2:= ~r'8'm(q)V8'r8r'(q) pl,
r',8' ~r8m(q) r'8,(Q,W).
(51)
2. Niing luQ'ngri~ng nhi~u dai con
Nllng luQ'ngrieng dill con tM l trong glin dung cMn dOng hQc b~c nhllt :
E{(k,z) = -~ L Vz~lm(k-k/,z-z')G~m(k,z'),
k',z',m
= E{,HF(k,z) + Ef.corr(k,z),
(52)
E{'JlF(k,z)=-~ L ~mlm(k-k')G~m(k'z'),
k',z',m
IIInfmg ItrQ'ngrieng Hartree-Fock khOng chfin,
(53)
.i - 1 ~ - I
)
[
1 - 1
]~I,con(k,z) - -73 L., Vtmlm(k k f (k -k' z - Zl)
k',z',rn /mlm,
xG~m(k'z'), (54)
Iii nfmg luqng rieng tucrngqUaD.
Phan Hartree-FockkhOng chfin elJa Dang luqng rieng dcrnh~t trong delicon thu l:
~f.IlF(k,C{(k))= - L~m'm(q)f;;lq'
(55)
q,m
D6i vai ham di~nmOinh~ duQ'ctlr(51) :
fh"lm(q,lJJ) =
1 - ~ ~rrm(q)Vrmlr(q) pL
(
)

Lr,j,k v,;rm(q)f;j(l- frj) 2
Xlml1ll - 2 n~ Wpl,lmlm .
Lr,j v,rrm(q);;;
D~ dan gillll trong vi~c tmh loan bilng s6 chUngtCliSlrd1}nggill dung c1!c-plasmon
(58)
2
wpl,lmlrn ~- ,
( )
- 1 - 2 W2
IOlmlrn q, W - W2 + Wpl,lrnlm - q,lrnlrn
(59)
W;,lmlm = W;"lm'm
(
1+ -1-
)
+
(
~2
)
2 .
X'mlm It
Khi d6, chung ta nh~n dugc pMn nang lugng rieng tl1<mgquan :
(60)
2',f.corr (k, e{(k))
'" . wfmlm
L t v,mlm(q)-
2
Wq,lmlm
q,m
[

mQt sl! kMc bi~t 16'0trong SBR cua cac diii con nay.
mnh 16 bi~u hi~n SBR theo n. K€t qua chUng to Sl!khac bi~t qua 16'0giiia gall
dung Hartree-Fock va gall dung ch:in dQng hQc khi tM gram nh6t 16'0.SI! khac bi~t
giiia 2 gAndung chi nho khi tM gram nh6t nM chUngto rang g!1ndung Hartree- Fock
kha di co th~ si'1dl:mgtrong cac h~ ban clankh6i.
Ket lui),n: Trong chuO'J1gnay, chung tOrdii danh gia duQ'cSBR tmng QWW cho
2 gAn dung va dft tim tMy mOt SIfkhac bi~t 16'0giiia gAn dung cMn dQng hQc va
g!1ndung Hartree-Fock, d~c bi~t lJ vUng n6ng dQplasma cao va tM gram nh6t 16'0.
Chung tOi dietsi'1d\lng mQt Valg!1ndung: g!1ndung cl!c-plasmon, gall dung Parle va
bo qua s6 hl;lngtan XI;lgiUa cac d,!i con. 01ung tOrdietchung to duQ'cdong gap cua
Bang Itrqng ri~ng tl1o'ngquan vao SBR la quan trQng va no khOng duQ'cbo qua, d<)c
bi~t tmng vung n6ng dQplasma cao, lJdo SI!eh:in tr<'1n~n quan trQng.
KliT LU~N
Chung tor dii trinh bay tmng lu~n an nay 2 10l;1ibar loan trong CalltrUe QWW la
bar loan h~ mQt hl;1tva h~ nhieu hl;ltma chUng th~ hi~n tfnh chat di~n va quang hQc
cua QWw. Chung tOrdii tlwc hi~n vi~c Hnh loan tr~n cac mOhlnh QWW khac nhau
19
: QWW be miJt, QWW cM nh$t va mO h1nh QWW vm rao tM ben parabol.
V6'i biii loan h~ mOth~t, trong cac ca'u trUcQWW co rao the!b1ftd6i xUng, bilng
phuang phap 1Va- Hartree chUng tOi dii giro quye!tvan d~ mang tfrih phuang pMp
luQ.ntrong vi~c sit d~ng phuang pMp bie!nthien de giro phuang trlnh SchrOdinger,
danh gia duQ'Chi~u Ungdi~n IrUUngIen cac mUGnang Iuqng cua di~ri tit, nang Iuqng
lien k!t vii h~ s6 pMn clfc cua t~p GMt, tUdo cho chUng ta tha'y duQ'cdang di~u dOng
hQcelm dlc hl,lttai trong cac d~ng c~ di~n tit sit d~ng ca'u trUcQWW. CluIng tOicling
Om tha'y mOtslf arm hubng m~ cua di~n IrUUngIen nang luqng lien ke!tcua exciton
trong cac QWW rao tM ben parabol.
Cho bili loan h~ nhi~u h~t, vm mO h1nh QWW rao the!ben paraboI, chUng tOi
dii tfnh duQ'cham phO niing luqng rieng va m~t dOpM cua di~n tit, BGR cua Qww
trong ph':lm vi gan dung PPA cua slf chiin dOng hQc, ma nhu dii bie!ttrong ca'u truc
kMi va QW, dOco cua khe dai dii giai thfch duQ'Cban GMtdich chuyen v~ vitng xanh

dltOngehd eho D. = 600 A.
30
~, ,
;-
I
;1
w
,
""'"
~ ~"'~"'"
~- "'"
""
II
.~
'30
""
'"
100
a(:J
tnnh 3 : NAnglUQ11gIi~nk€i Eb nhlt hAmcu. kfeh thlt"" a
0
cu. QWW ehii nhA'v(ri kfeh Ihlt"" b = 150 A, ',p eMI b
:1:0 = YO= OvAeltOngdQdj~ntrttbngF = JOOkV!em.
8 = 45°. DltOngl;~nehorAolh€hiillh"Vo = 0.4eV.
dltOng g,eh eho rAo Ih€ vO h".
"
"
,//
/'
////

mnh 4 : H~ s6 phAn eye <>p nhlt hAm CURg6c 8 g;iin dl~n
. 0 0
trltOngvAtrye:l:choa = 100 A,b = 50 A.:l:O =YO =O.
vAF = 200kV!cm. Dttbngli~n:rAothl!hiillh,,(Vo =
O.4eV), dltOngg,ch:rAnthl!vOh".
21
0.11L "'"
f om,
';J- 01"
om
~
,
I
;;!
' ',
/ "
,
,
';~-~'" ",
// ""
\
' \
,
'"
"1
.",
.n
"
Y.(;)
H1nb 5 : NOng1"<;1I1glito kEt Eb nh" him CUBvi tr! t~pch<it

mob 6 : NOng1"<;1I1glito kt"1Eb nb" him theo kich th""" a
CUBQWW eM nh~t do thEbiJub", Vo = O.4eV tho a X
b = eonst vA"'0 = 110 = O. I)~g li~n : a X b =
0 0
100 A X100 A vAF = 0; d~g g~eb-ehlin : a X b =
1001 X1001. F = 100kV!em vAe = 90°; d"lmg
0 0
g~ch : a X b =200 A X200 A vAF = 0; d"lmg ohlin
0 0
: a X b = 200 A x200 A vAF = 100kV!em vii
e = 90° . Inoh btn tmng : khu6:h d~ CUBd"lmg g~ch.
"
"
!
.r
/
. . /////
/"
,/

.
.
In(R)
mob 8 : Nilng 1"<;1I1glito kEt Eb nh" him CUBn. O"lmg Ii~n
tho F = lOOk V lorn. d"lmg g~ch tho F = 75kV!cm vii
d"lmgehlin tho F =50kV!em,
22
~
a:
a

-2
a
<5
~
/1
ji
15
0
.15
.10 .5 10 15
mfR
mob 10: HAmm,' dQph6 di~ tit A.(O, "') nhllbAmcuo '"
cook = O.cac tbarn s6 gi6ng ohll hlnh 3.1.
.10
.IS
, ~
.35
"""'""""""""""""""""""""""""""""""""""""" !
,L
. w
100 150 3JO 2W 300
20
T(K)
mob 12 : DQ lAi chul!n h6o kJ1c do !:>.Eo nhlliA mQl hAm cuo
nhi~tdQchon =10Rbdco6ngdQplasm.kh4cnhoILDlllmg
lil!o : gl!n dung d<)ng hQCday du, dlllmg g~h : gl!n dUng d<)ng
hQC'0 vAd"lmg chdin : gl!n dUng '0 giA-tinh. cac d"lmg nh,t
chn nao =0.1, cAcdlllmgdAmcho naO = I.
23