L. Besombes et al., PRL93, 207403, 2004 Single exciton spectroscopy in a semimagnetic nanocrystal J....
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Transcript of L. Besombes et al., PRL93, 207403, 2004 Single exciton spectroscopy in a semimagnetic nanocrystal J....
L. Besombes et al., PRL93, 207403, 2004
Single exciton spectroscopy in a semimagnetic nanocrystal
J. Fernández-RossierInstitute of Materials Science, University of Alicante, SPAIN
Talk available in: www.ua.es/jfrossier/personal
Absorption Emission
CdTe nanocrystal
CdTe nanocrystal+ 1Mn
Goal: Calculate PL and quantum information
Spin relaxation
PLPL
6NMn
S=5/22S+1=6
Method :1) Calculation of one-body wave
functions (for a given dot)2) Evaluation of many body
exciton-Mn spin Hamiltonian3) Exact diagonalization of GSM4) Exact diagonalization of XSM5) Linear reponse theory
Ground State Manifold (GSM)
Exciton States Manifold (XSM)
4x6N
6N
-1 +1-1 +2
1
4
)()(
NMnGSM Qbits
1 6 2
2 36 5
3 216 7
4 1296 10
FORMALISM
I
IBII
IIII MBgMMJH
',
'',0
Ground State Manifold (GSM)
NN SSSS ...),...,( 11 GEGH G0
4 6N
e
h
IIhIh
VB
IeI
IeCB
xSMJH
xSMJHH
)(
)(1
XEXHH X 10
Exciton States Manifold (XSM)
6N
SPIN ORBIT INTERACTION )(
)(
Iz
Iz
IhI
xSM
xSM
Heisenberg
Ising
Valence band Spin orbit: Ising
coupling
)(
)(
Izz
I
IhI
xSM
xSM
SHAPE MATTERS:
Quenching of transverse Hole-Mn exchange
GSM and XSM spectrum
E(meV)
1 MnNG=6NX=24
2 MnNG=36NX=244
3MnNG=216NX=864
E(meV)
Magnetic Field (0,0,5)
XEXHH X 10 XEXHH X 10
XX
X
TkE
XXX Z
eEPPL
BX /
)()(
Photoluminescence (PL) Theory
G
GXX EEGpX 22
Spontaneous Emission from X to G
Energy conservation
OpticalSelection rules
SPIN BLOCKADE
PL SPECTRUM
Occupation of excited state
Thermal like occupation
Energy (meV)
PL, theory PL, experiment
PL: results
)()(
OPTICAL SPIN BLOCKADE
Franck Condon=Spin Blockade
Standardoptical selection rule
GS
M
XSM
G
GXX EEGpX 22
22
11
2),...,(),...,( XpgSSSSGpX NSNG
Photon measurement=SPINMEASUREMENT
24*6=144 XSM to GSMOnly 12 are allowed
PL, experiment
)()(
N=3. Narrowing and shift
0T
2T
4T
6T
8T
10TP. S. Dorozhkin,Phys. Rev. B 68, 195313 (2003)
Conclusions
• Model Hamiltonian gives good account of PL experiments:– Single Mn – Broadening and narrowing of lines– Voigt wider than Faraday
• Optical detection of quantum state of N=1,..4 spin S=5/2
in semiconductor nanocrystal.
Related papers:1) JFR, in preparation2) JFR, L. Brey, Phys. Rev. Lett. 93 117201 (2004)3) G. Chiappe, JFR, et al, Condmat/0407639