A. Nitzan, Tel Aviv University
LIGHT AND CURRENT
In molecular condution junctions
ThanksW. Belzig, A. Burin, B. Feinberg, M. Galperin, J. Gersten, O. Godsi, P. Hänggi, M. Jouravlev, S. Kohler, K. Kaasbjerg, Lehmann, G. Li, M. Oren, T. Seideman, M. Sukharev,
2014 CaSTL Summer School, Irvine
MOLECULAR JUNCTIONS
HOT SPOTS
MOLECULAR JUNCTIONS
2 2( )
/ 2
kL kRk
k kL kR
E
E E
T
%
1
21/24
( ) exp 2 ( )B
s
sE m U x E dx
T
h
J. G. Simmons, J. Appl. Phys. 1963 (cited by 2571)
BU x
) ( )( ( )L Rf E fe
I dE EE
Th
fL(E) – fR(E) T(E)
eF
fL(E) – fR(E)
T(E)eF
I
FWeber et al, Chem. Phys. 2002
g
Landauer formula
1( ) exp ( ) / 1K K Bf E E k T
h
INELSTIC ELECTRON TUNNELING SPECTROSCOPY
V
V h
V
h0h0
incident scattered
Light Scattering
out in-0 in
out in-0 in
out in-0 in
Localization of Inelastic Tunneling and the Determination of Atomic-Scale Structure with Chemical Specificity
B.C.Stipe, M.A.Rezaei and W. Ho, PRL, 82, 1724 (1999)
STM image (a) and single-molecule vibrational spectra (b) of three acetylene isotopes on Cu(100) at 8 K. The vibrational spectra on Ni(100)are shown in (c). The imaged area in (a), 56Å x 56Å, was scanned at 50 mV sample bias and 1nA tunneling current
Recall: van Ruitenbeek et al (Pt/H2)- dips
Dephasing and relaxation are important
Relative timescales are important
Electron-vibration interactions may be important
Transient localization may be important
Interaction with light
R.M Hochstrasser and C. A. Nyi,J. Chem. Phys. 70, 1112 (1979)
Azulene in Naphthalene matrix (4-35K)
Molecular conduction
molecule
•Fabrication
•Stability
•Characterization
•Funcionality
•Control
MOLECULAR JUNCTIONS
Molecular electronics and plasmonics: The interaction of molecular conduction junctions with light
Junction spectroscopy
(1) Local radiation field associated with the new boundary conditions
(2) Surface “selection rules”
(3) Finite lifetime for electron on molecule (broadening due to electron transfer interaction with metal)
2 2( )
/ 2
kL kRk
k kL kR
E
E E
T
%
(4) Finite lifetime for electronic excitation due to dipolar coupling (energy transfer to e-h pairs in metal)
Junction spectroscopy(5) With bias – partial occupation may change absorption and scattering spectra
(6) Current may drive light and light may drive current
(7) Heat may develop and temperature change may affect spectra
ABSORPTION LINESHAPE
21
6
,1 ,1
,2 ,2
2
10
0.1
300
0.01
0.2
P
NL NR
ML MR
ML MR
eV
eV
B B eV
T K
eV
eV
Fig.2 The absorption current (photons/s). The molecular electronic levels are assumed pinned to the right electrode, i.e. the bias shifts upward the electronic states of the left electrode.
Transfer Rates
{ }l
1
V1r
r l
V1l
2
1 12r
R r RE E
E V
1 1
1 22
1 1 1
( )/ 2
L R
L R
EE E
T
= 1 if E=E1 and G 1L=G 1R
2
1 12 ; ,k
K k KE E
E V K L R
VV V
L
{ }l
R
d
~de 1
large d1~c d d
Ohm’s law!
Dependence on bridge length
Ne
11 1
up diffk k N
Segal, AN, Davis, Wasielewski, Ratner J. Phys. Chem. B, 104, 3817-3829 (2000)
DNA (Giese et al 2001)
J. AM. CHEM. SOC. 132, 435(2010)
FRET(Fluorescence (Forster) Resonance Energy Transfer)
R
2
1 2
3~kR
R
6 4
1 1~dS
R R
6 3
1 1~dV
R R
0
1
1 /n
efficiency
r r
FRET: n=6
SET : n=4
R
6 6
1~Surface Area
dSR R
6 6
1~particle volume
dVR R
R>>Particle size
2~R totk
23; ~ Im~ent particle
k d r E M. Sukharev, N. Freifeld and AN, J.Phys.Chem C, 2014
2
2
1E n n 3n n
ikr ikre ik ek
r r rr
r r r
Electric field from an oscillating dipole in free space
2
2 2 4
1 1 1E ~ 1
r kr kr
2
2 2 4
4 1 1E ~
r kr kr
P
Dynamical equations0 = ,H
Et
rr
0 = ,H
Et
rr
0 = ,E
H Jt
rr r
2
2( ) =
p
ri
20= ; = ; = p
JaJ bE
ta b
rr r
metal
J P t r r
ˆ= ; TrP n r r r r
molecules
ˆ ˆ ˆˆ ˆ= [ , ]d
i H idt
h h
0ˆ ˆ= ( )H H d E t
r r
M. Sukharev and AN Phys.
Rev. A 84, 043802 (2011)
LIGHT ON JUNCTIONS
SWITCHES
Light operated molecular switch
NON RESONANCE EFFECTS
Nano Lett. 9, 1615 (2009)
RESONANCE EFFECTS
mg=7 D me=31+/-1.5 D
mg=5.5 D me=15.5+/-1.5 D
mg=7 D me=30+/-1.5 D
CHARGE TRANSFER TRANSITIONS
S. N. Smirnov & C. L. Braun, REV. SCI. INST. 69, 2875 (1998)
LUMO |2>
HOMO |1>
L
R
Light induced current in molecular junctions-resonance mechanism
Current induced light
E21=2eV
GM,1= G M,2=0.1eV
G N=0.1eV
Observations: Flaxer et al, Science 262 , 2012 (1993),
Qiu et al, Science 299 , 542 (2003),
G. Hoffmann et al, Phys. Rev. B 65, 212107 (2002)
Yield
Intensity
Emission yield from 9-10 dichloroanthracene on a quartz lens coated with ITO (Indium Tin Oxide), a transparent conductor.
Flaxer et all, Science, 262, 2012 (1993)
Schematic sketch and
energy diagram of a STM
junction, in which a single
magnesium porphine
MgP its molecular
structure shown in
molecule is adsorbed on a
thin insulating alumina
film grown on a NiAl110
surface.
Wu, Nazin and Ho, Phys. Rev. B 77, 205430 (2008)
Spatial dependence of the
emission spectra from the
same molecule as in Fig. 2.
The locations of the STM
tip where each spectrum
was collected are marked in
the STMimage of this
molecule inset.
Inelastic tunneling
spectrum of the
same electronic
transition observed
on the left by its
emission spectrum.
No vibrational
resolution can be
achieved probably
because many
vibrations contribute
h
Photon emission from biased junctions
V
V h
V
Detector
sensitivity
The phase structure (chirp) of the pulse determines the temporal
ordering of its different frequency components that enables us to
control molecular dynamics.
B. Fainberg and A. NitzanPRB, 76, 245329 (2007)
|1,0>
|2,0>
|1,w>Vp
t
|1,w(t)>
Total electronic population inversion can be achieved using coherent light-matter interactions like adiabatic rapid passage (ARP), which is based on sweeping the pulse frequency through a resonance.
0( ) ( )t t t ((
w0 = e2 - e1
h0h0
Raman Scattering
h0h0
incident
scattered
Stokes
incident
scattered
anti-Stokes
( ) ( ) ( ) ( ) ( )0
ˆ ˆ ˆ ˆ ˆ ˆ ˆ= e et b e h e pH H V V V V V
v v
†
=1,2
†
{ ,
†
{ }
0††
, }
ˆˆ ˆˆ ˆˆ ˆ ˆ ˆˆ = ˆk k k
k
m m
R
m
L i fm
c cd d ab abH b b
v v v
( ) ( )( )
= ,
†
;
†ˆ ˆ= ˆˆ ˆetmk
etetkm mk
K L R K m
km
k
V V Vd cdc
†( ) ( )
=1,2
ˆ= ˆˆ ˆe em
m
m mQ dV dV v
v
v
( )( )ˆ = ˆ ˆbb QU QV
v
v
v
( ) ( )( )
1 2 2 1
† †2 1 1 2
† †
2 111 2
2ˆ ˆ ˆ ˆˆ= ˆ ˆ ˆˆ
k kk
e h e he hk k k k
kk
k
c c cV V Vd d dc d
†2
†( ) ( ) *( )
{
1 2
,{
†
}}
1ˆˆ = ˆ ˆ ˆ ˆˆe p e p e p
M
i f
V a aU U d dd d
Molecule
Metals
Vibration
Thermal
bath
photons
RAMAN SCATTERING
Current
Total Scattering
Stokes and antistokes intensities
RAMAN SCATTERING
=ln /
vS aS
i i v i i v
TJ J
Temperature from S-As ratio
Comparing temperature by two methods
frequency renormalization, damping and heating of
vibrational modes in nanoscale junctions
“Figure 3b shows another feature that is observed with some regularity in such
junctions: a systematic shift in energy of 15 cm21 is observed for most (Stokes)
vibrational modes as a function of V. This is an example of a Raman Stark shift.”
Ward, Corley, Tour, Natelson (Nature Nanotechnology 1/11)
OPV3
d–f, The same data for the OPV3 device used for Figs 1 and 3. The data in d,e,f demonstrate that bias-
driven electronic heating is also detectable in junctions that show optical pumping and bias-driven
vibrational heating.
Electronic heating under bias. a,
Effective temperature (blue; left
axis) and dissipated electrical power
(red; right axis) versus bias voltage V
in a nominally bare device. Error
bars are described in the text. Inset:
current/voltage curves for this
device. Error bars are described in
the text. b,c, Raman response
shown as a Raman signal (in CCD
counts) as a function of voltage and
Raman shift (b), and as the Raman
intensity (in CCD counts) as a
function of Raman shift (c) at three
different voltages (blue lines); the
green lines are best fits to the data
given by equation (2). Only the anti-
Stokes signals are shown in b and c.
This device shows no molecular
Raman peaks, and is considered a
‘clean’ junction.
Ward et al, J. Phys. Chem. Lett. 2011, 2, 2110–2113
Raman scattering from biased molecular
conduction junctions: The electronic
background and its temperatureM. Galperin and AN , PRB 84, 195325 (2011)
1
2TSS
K K KKf E f E E f E f E
, 02
T SS effK K K
dEE E f E f E T
M. Galperin, AN J. Phys. Chem. Lett. 2011, 2, 2110–2113
Electron-vibration interactions
Linear el-vib interaction:
Quadratic el-vib interaction:
Frequency shifts due to charging
x
Kristen Kaasbjerg, Tomas Novotny and AN, PRB 88, 201405(R) (2013)
OPV3 junction
El-vib couplings:
vibrations and couplings calculated with DFT for the neutral molecule (adiabatic approx.)
field effects neglected
no nuclear relaxation
OPV3 spectral function
Off-resonant single-level junction
Parameters
Lu, Hedegard, Brandbyge, PRL 2011
Summary Light in junctions Optical conduction switching Light induced current Current induced light Raman Scattering Vibrational spectroscopy in
conduction junctions Exciton-plasmon interactions Energy transfer rates –
molecule to nanoparticle
