shot noise and conductance spectroscopy on a single molecule junction oren tal michael krieger, rik...
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Shot Noise and conductance spectroscopy on a single molecule junction
Oren TalMichael Krieger, Rik Hortensius, Bas Leerink
Robert Thijssen, Darko Djukic and Jan van Ruitenbeek
Leiden University,Netherlands
Capri Spring School 2007
Electron-Vibration Interaction
-80 -60 -40 -20 0 20 40 60 80-0.2
0.0
0.96
0.98
1.00
d2 I/dV
2 (ar
b. u
nits
)
d
I/dV
(G0)
Bias voltage (mV)
Inelastic Electron Tunneling SpectroscopyTypically low conductance ~10-5G0
Djukic et al. Phys. Rev. B (R). 71 (2005), 161402Thygesen et al. Phys. Rev. Lett. 94 (2005), 036807
Point Contact SpectroscopyTypically high conductance ~1G0
C2H2
Stipe et al. Rev. Sci. Inst.70 (1999), 137
H2
heGo 22
-60 -40 -20 0 20 40 600.97
0.98
0.99
dI/d
V [G
0]
Bias Voltage [mV]
Pt+H2O
Conductance curves of different molecular junctions
-60-40-20 0 20 40 600.22
0.24
0.26
0.28
dI/d
V [G
0]
Bias Voltage [mV]
Pt+H2O
-80 -40 0 40 800.30
0.32
0.34
0.36
0.38
0.40
dI/d
V [G
0]
Bias Voltage [mV]
Ag+O2
-60 -40 -20 0 20 40 600.92
0.94
0.96
0.98
1.00
dI/
dV [G
0]
Bias Voltage [mV]
Pt+H2
Step up
Step down
heGo 22
“step up” to “step down” shape transition as a function of conductance
-60 -40 -20 0 20 40 600.45
0.50
0.55
0.60
0.65
0.70Pt+H2O
dI/d
V [G
0]
Bias Voltage [mV]
Step size and direction in conductance curves
-60 -40 -20 0 20 40 600.45
0.50
0.55
0.60
0.65
0.70
dI/
dV
[G0]
-60-40-20 0 20 40 600.22
0.24
0.26
0.28
Bias Voltage [mV]
-60 -30 0 30 600.97
0.98
0.99
L. de la Vega, A. Martín-Rodero, N. Agraït, and A. Levy Yeyati, PRB 73, 075428 (2006)
Low Transmission
5.0
HighTransmission
5.0
(M. Paulsson et al. PRB 72, 201101R (2005) similar 0.5 transition)
Deviation from a single channel model
Single channel model:transition between “step up” to “step down”at 5.0
Do we have more then a single transmission channel for a Pt-H2O -Pt junction?
Shot Noise measurements
In our experiment:transition between “step up” to “step down”at GoG 65.0
i ih
eG
22
Shot noise in Pt+H2O single molecule junction
6
The transition between to occurs above 5.0 5.0 GoG 01.052.0
0.0 0.1 0.2 0.3 0.4 0.50
1
2
3
4
Fullshotnoise 1=0.48
2=0.04
Exc
ess
nois
e [1
0-2
6 A
2/H
z]
Bias Current [A]
GoG 01.052.0
0.0 0.2 0.4 0.6 0.80
1
2
3
4
1=0.95
2=0.05
Fullshotnoise
Exc
ess
nois
e [1
0-26
A2 /
Hz]
Bias Current [A]
GoG 01.000.1
At the main transmission channel has 5.0GoG 01.052.0
Conclusions
Point contact spectroscopy : The effect of electron - vibration interactions on the differential conductanceis inverted at a certain conductance. Shot noise measurements: More than a single transmission channel through the Pt-H2O-Pt junction
Using the combination of point contact spectroscopy and shot noisemeasurements the apparent deviation from the relevant models could beresolved.
Open question: what is the role of transmission channel mixing due to electron – vibration interactions?
Acknowledgments
Prof. Jan van Ruitenbeek
Michael KriegerRik HortensiusBas Leerink Robert ThijssenDarko DjukicChristian Martin Sander Otte
Ruud van EgmondBert Crama
Electron-Phonon Interaction
V
dI/dV
0V
Point Contact SpectroscopyTypically high transmission probability
V
dI/dV
0V
Inelastic Electron Tunneling SpectroscopyTypically low transmission probability
LeV
R
R
E
11
k
E
eV
e
e
i i
i iiI eIS
)1(
2
i ih
eG
22
Shot noise in point contacts
5 10 15 20
4x10-18
6x10-18
8x10-1810-17
0.8A
G=1.00+/-0.01G0
Tot
al n
oise
[V2 /
Hz]
Frequency [KHz]
0A
Lock-in
I-V
Spectrum Analyser
100100
1000 1000
100MFaraday cage
dipstick
PC
cryostat
battery
S1
S2
0.0 0.2 0.4 0.6 0.80
1
2
3
4
1=0.95
2=0.05F=0.095
Fullshotnoise
Exc
ess
nois
e [1
0-26
A2 /
Hz]
Bias Current [A]
Shot noise in Pt+H2O single molecule junction
6
0.0 0.1 0.2 0.3 0.4 0.50
1
2
3
4
Fullshotnoise 1=0.48
2=0.04F=0.554
G = 0.52 +/-0.01G0
Exc
ess
nois
e [1
0-2
6 A
2/H
z]
Bias Current [A]
At about G=0.5G0 the main transmission channel has 5.0
The transition between to occurs above 5.0 5.0 GoG 01.052.0
GoG 01.052.0 GoG 01.000.1
0 2 4 60
1000
2000
3000
Vb=0.1V
nu
mb
er
of c
ou
nts
Conductance (G0)
Pt
Conductance histograms: Pt
8 10 12 14 16 180
1
2
3
4
5
Co
nd
uct
an
ce (G
0)
Piezo voltage (V)
Pt
Conductance histograms: Pt+H2O
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00
500
1000
1500
2000
2500
30000.96G0 Vb=0.2V
1.16G0
Pt + H2O
No
. o
f co
un
ts
Conductance [G0]
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00
500
1000
1500
2000
2500
3000
1.00G0
0.20G0
Vb=0.1V
0.60G0
Pt + H2O
No
. o
f co
un
ts
Conductance [G0]
>at lower bias voltages lower peaksare more pronounced.
Conductance traces
0.30
1
2
3
4
C
on
du
cta
nce
(G0)
Piezo voltage (V)
Pt+H2O
0.2 0.30
1
2
3
4
Co
nd
uct
an
ce (G
0)
Piezo voltage (V)
Pt+H2O
0.2 0.3 0.40
1
2
3
4
Co
nd
uct
an
ce (G
0)
Piezo voltage (V)
Pt+H2O
0.2 0.30
1
2
3
4
Co
nd
uct
an
ce (G
0)
Piezo voltage (V)
Pt+H2O
>Pt-H2O-Pt configurations with higher conductance then 1G0 (?)