exciton-plasmon interactions and fano resonances in nanostructures · 2010-09-14 ·...
TRANSCRIPT
![Page 1: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/1.jpg)
Exciton-Plasmon Interactions and Fano Resonances in Nanostructures
Alexander Govorov
Department of Physics and Astronomy, Ohio University, Athens, Ohio, USA
Supported by: NSF, Air Force Research Office, A. v. Humboldt Foundation,
BNNT Institute at Ohio U.
![Page 2: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/2.jpg)
Collaborators:
Pedro Hernandez, Ohio U.Fan Zhiyuan, Ohio U.Wei Zhang, Ohio U. (now in China)
![Page 3: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/3.jpg)
Nanoparticles as building blocks Interaction between nanocrystals
Exciton + plasmon + photons
Linker(polymer)
liquid
Quantum emitter
Amplification or suppression of PL
+++
+---
-
excitonplasmon
AuCdTe
+++
+---
-Au
CdTe
plaser
emissionexcp E
![Page 4: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/4.jpg)
Incoherent exciton-plasmon interaction
2, int
2 2ˆ( ) | 0; ;0 | ( ) Im[ ( )]non rad metal exc exc f excf T
f V exc
Field enhancement factor:
2
2
2
)( photon
tmetalno
tactual
EE
EP
1exc
0exc
0
Metal NPSemiconductor NP
+++
+-- -
-Au
CdTe
Book: Joseph R. LakowiczPrinciples of Fluorescence Spectroscopy
Energy transfer (FRET) rate:
00 0( ) ( )exc
rad exc non rad transfer exc ldn P n P I
dt
![Page 5: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/5.jpg)
Slocik, J.M.; Govorov, A.O.; and Naik, R.R., Supramolecular Chemistry, 2006.
N Au-NP -- CdSe-NP
Number of Au NPs
![Page 6: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/6.jpg)
NAu=1 NAu=2 NAu=4 NAu=6
400 500 600 700 800 900 10000.8
0.9
1.0
1.1
1.2
NAu=4,2
NAu=1NAu=6
Ena
hnce
men
t fac
tor
Wavelength, (nm) 0 1 2 3 4 5 6 7 80.0
0.2
0.4
0.6
0.8
1.0
1.2
theory
exper
Number of Au NPs, NAu
emiss=610 nmlaser=400 nm
Em
issi
on ra
tio A
(NA
u)
0
0
( )(0)
emiss Au NPs
emiss transfer
I NAI N
Emission ratio:
Govorov, et al., Nano Lett., 2006
![Page 7: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/7.jpg)
Coherent interactions. Fano effect
1
2 k
0V v
w
2 2 20
2 2 2
2
0
( )2
E v qAbsw
wV wqv
-40 -20 20 40
0.05
0.1
0.15
0.2
0.25
0.3
12
Absorption
Detuning,
X-ray absorption spectrum of He
-40 -20 20 40
0.05
0.1
0.15
0.2
0.25
0.3
![Page 8: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/8.jpg)
Fano effect in He
2 1s1 k
0V v
w
X-ray absorption spectrum of He
![Page 9: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/9.jpg)
Fano lineshapes
1
2 k
0V v
w
2
2 2
122
0
( )qAbs
wV wqv
-10 -5 0 5 100.0
0.5
1.0
1.5
-10 -5 0 5 100.0
0.5
1.0
1.5
Abs
orpt
ion
-10 -5 0 5 100.0
0.5
1.0
1.5
q=0.01
q=2
Detuning
q=100
12,
![Page 10: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/10.jpg)
k
++
++
---
-
exciton plasmons
MNPSQD
Coulomb interaction
kCoulkk
Coulkkk
k accUaccUaaccEccEH ˆˆˆˆˆˆˆˆˆˆˆˆˆ21
*122221110
1
2
exciton plasmon states
ground state
Colloidal nanocrystals
![Page 11: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/11.jpg)
Two paths for excitation of plasmon interference effect (Fano effect)
Optical absorption
k
1
2
exciton plasmon states
ground state
++
++
---
-
exciton plasmons
MNPSQD
Coulomb interaction
![Page 12: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/12.jpg)
Fano effect
1
2 k
0V v
w
-40 -20 20 40
0.05
0.1
0.15
0.2
0.25
0.3
12
absorption
2 2 20
2 2 2
2
0
( )( )2
E v qAbsw
wV wqv
![Page 13: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/13.jpg)
Light
ttV
tVHH
HHit
accUaccUaaccEccEH
opt
opt
kCoulkk
Coulkkk
k
cos)(ˆ)(ˆˆˆ
ˆˆ)ˆˆˆˆ(ˆ
ˆˆˆˆˆˆˆˆˆˆˆˆˆ
0
0
21*
122221110
Er
Strong de-coherence in the metal NP (fast relaxation of plasmon)
Electromagnetic enhancement due to the plasmon
++
++
---
-
exciton plasmons
MNPSQD
![Page 14: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/14.jpg)
W. Zhang, A. Govorov, et al., PRB 2008.
Dipole limit:
tot MNP SQDQ Q Q
![Page 15: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/15.jpg)
12
10
1
metal NP semiconductor NP
metal NPR nm
meV
100nm
2.0 2.2 2.4 2.602468
101214
Photon energy (eV)
Ext
inct
ion,
(1
08 cm
-1 M
-1)
![Page 16: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/16.jpg)
W. Zhang, A. Govorov, et al., PRB 2008.
In the regime of strong de-coherence: Strong anti-resonances in
absorption and light scattering
Weak lines become visible as anti-resonances
Multipoles are important
100nm
NPtorsemiconducNPmetal
CdTe-Au complex
12nm
tot MNP SQDQ Q Q
12 110metal NP
meVR nm
![Page 17: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/17.jpg)
Nonlinear Fano effect
1
2 k
0Vv
w
Strong light fieldTransition 1 2 is partially saturated
1 2 22 11Absorption
![Page 18: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/18.jpg)
Experiments in MunichA dot with weak tunnel coupling to a continuum
Fano factor
Narrow exciton resonances
Self-assembled quantum dots at low temperatures
GaAsInAs
Quantum well
1Fanoq
AlGaAs
![Page 19: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/19.jpg)
-0.5
0.0
0.5
1.0
-50 0 50 -50 0 50 -50 0 50 -50 0 50 -50 0 50-50 0 50
-0.5
0.0
0.5
1.0
0.41µeV 2.1µeV 6.9 µeV 16 µeV9.5 µeV
0.33 nW 168 nW90 nW8.3 nW
22 µeV
481 nW 935 nW
L - 01 (µeV)
Nor
mal
ized
ext
inct
ion
Martin Kroner, Khaled Karrai, at al., experiments
Theory
M. Kroner, A. O. Govorov, S. Remi, B. Biedermann, S. Seidl, A. Badolato, P. M. Petroff, W. Zhang, R. Barbour, B. D. Gerardot, R. J. Warburton & K. Karrai, Nature, 2008.
Nor
mal
ized
diff
eren
tial a
bsor
ptio
n
powerNonlinear Fano effect
![Page 20: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/20.jpg)
Low power High power
At low power, the natural broadening prohibits observation of weak processes
At high power, we can observe weak coherent processes
The discrete resonance is saturatedTransitions to the continuum become more important
powerabso
rptio
n
Discrete
continuum
laser
1Fanoq
![Page 21: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/21.jpg)
metal NP molecule
Light
0
0metal NP
molecule
CD
CD
Optical chirality (circular dichroism)
![Page 22: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/22.jpg)
Circular dichroism spectroscopy
0
10log lcplcp lcp
lcp
lcp rcp
CD lcp rcp
IA L c
I
A A A
0( )lcp rcpI ( )lcp rcpI
k
Chiral objects: No mirror symmetry planesExample: Helix
![Page 23: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/23.jpg)
1
2
molecule density of states of NP
photons
Coulomb
NP
dye
m
R
NPa
k
![Page 24: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/24.jpg)
150 200 250 300 350 400 450 500-40
-20
0
20
40
60
80
CD
,
(cm
-1M
-1)
Wavelength (nm)
plasmon-induced
*,
*, ||
*, ||n
150 200 250 300 3500
2000
4000
6000
8000
Wavelength (nm)
Ext
inct
ion
(cm
-1M
-1)
Ag
*,
*, ||n
*, ||
-helixAg NP
W. Moffitt, J. Phys. Chem. 25, 467 (1956).
Chromophore excitons are delocalized in a helix structure
z
x
y
Govorov, A.O.; Fan, Z.; Hernandez, P.; Slocik, J.M; Naik, R.R., Nano Letters, 2010.
![Page 25: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/25.jpg)
Purely plasmonic CD
Z. Fan, A. O. Govorov, Nano Letters 2010.
![Page 26: Exciton-Plasmon Interactions and Fano Resonances in Nanostructures · 2010-09-14 · Exciton-Plasmon Interactions and Fano Resonances in Nanostructures Alexander Govorov Department](https://reader030.vdocuments.net/reader030/viewer/2022040806/5e476eff217a17469e18890e/html5/thumbnails/26.jpg)
The exciton-plasmon interactions
Linear and nonlinear interference effects
Plasmon-induced CD
Conclusions
Low power High power
Ag
150 200 250 300 350 400 450 500-40
-20
0
20
40
60
80
CD
,
(cm
-1M
-1)
Wavelength (nm)
plasmon-induced