SubProject I: Coupled Quantum Dots

1
Sub-Project I Coupled Quantum Dots
Ron Cosby, BSU Yong Joe, BSU Greg Van Patten,
OU Sergio Ulloa, OU
2
Greg Van Patten Sergio Ulloa
(chemistry ) (physics)
Condensed Matter and Surface Sciences Program and
Nanoscale and Quantum Phenomena Institute Ohio
University, Athens, OH
Supported by US DOE NSF
3
Self-assembled quantum dots
Stranski Krastanow islands MBE
in-plane densities 1010 - 1011 cm-2 size
variations lt 10 sharp photoluminescence
features, frequency ? size
4
Colloidal quantum dots
Quantum Dot Corp. Evident Technologies

• Chemical synthesis
• CdSe, CdS, InP, etc
• Size 5nm diameter
• Use as biotags

5
(No Transcript)
6
trioctylphosphine oxide (TOPO) 11A
A acceptor larger dot
D donor smaller dot
Crooker et al PRL 2002
CQDs have better characteristics than biological
light harvesting compounds, eg LH2
7
(a) PL decays from a dense film of monodisperse
R12.4A/9A CdSe/ZnS NQDs at the energies
specified in the inset. Inset cw PL spectra
from film (solid) and original solution (dashed).
(b) Dynamic redshift of the peak
emission. Inset PL spectra at the specified
times.
Crooker et al PRL 2002
8
Energy/exciton transfer in quantum dot linear
array
Al-Ahmadi SU
exciton probability at each dot
Vct/2p
efficient interdot transfer rate
9
Coherent control of quantum dot photodiodes
(Zrenner et al Nature 2002)
Rabi oscillations in photocurrent coupled
quantum dots
10
How does the device work?
tradgt ttunnel
Zrenner et al. Nature 2002
11
How does the device work?
12
Mesoscopic optical spectrum analyser
QCSE
13
Rabi Oscillation in the photocurrent
14
What are we doing... Villas Boas,
Govorov, SU
Estimate the tunneling time
Which one tunnels first, electron or hole? After
one tunnels, how long before the second tunnels?
What is the effect of Coulomb interaction
(excitonic corrections)?
Luyken et al. APL 1999
Modeling using a density matrix formalism and
tunneling

• How much was population inverted?
• Can this be controlled by gates? Detuning?
• Role of coupled quantum dots?