Biomedical Engineering Reference
In-Depth Information
10.8
Competing Effects of Tunneling and Forster Energy
Transfer in Monoexcitons
Let us consider the general signatures of charge tunneling and investigate what are
the overall features of FRET according to the level diagram in Fig.
10.5
a. To this
end we have chosen the QD structural parameters (see Appendix Table
10.2
), such
that excitons
0
01
X
and
1
10
X
are initially in near resonance (strongly coupled).
Figure
10.5
a shows the level diagram corresponding to the effective Hamiltonian
in (
10.13
). With this Hamiltonian we can construct a level anticrossing population
map for the vacuum state
0
00
X
. Figure
10.5
b shows the LACS results for a QDM with
an interdot distance of
d
=
8
.
4 nm, assuming negligible F orster coupling among
10
10
X
and
0
01
X
exciton states (
V
F
=
0). With these assumptions, the electron and hole
tunnelings,
t
e
and
t
h
, are obviously the dominant interdot couplings. On the other
hand, coupling to the radiation field,
Ω
T
(
B
)
, has the effect of dressing all exciton
states, effectively coupling the direct states very weakly via higher order tunneling
Fig. 10.5
(
a
) Single-exciton energy level diagram showing the relevant couplings with the empty
QDM state,
00
00
X
.(
b
)and(
c
) Show occupation maps of vacuum state
00
00
X
in (
10.13
), exhibiting
10
10
X
,
01
01
X
, and indirect excitons,
01
10
X
,
10
01
X
, have nonzero
features as indicated, where direct,
occupation; for vanishing (in
b
) and nonzero
V
F
(
c
). Notice sizeable
Δ
F
splitting at high fields,
away from tunneling anticrossings. Rolon, J.E., Ulloa, S.E.: Phys. Rev. B
79
, 245309 (2009).
(2011) American Physical Society
