giant thermopower and figure of merit in single-molecule
TRANSCRIPT
Giant Thermopower and Figure of
Merit in Single-Molecule Junctions Colin Lambert,
Lancaster University
.Lancaster
Manchester .
R. Nichols
S. Higgins
•Durham
M. Bryce
M. Turner
An idea !
.Lancaster
Destructive interference = power !
A different idea!
• Introduction to single-molecule electronics
• Hunting for Fano resonances and signatures of room-temperature quantum interference
• Geometric control of Fano resonances • Giant thermopower and figure of merit in single-
molecule devices induced by Fano resonances
Single-molecule
LEGO
Anchors
Linkers
N N
NN
Zn
Ar
Ar
N
N N
NN
Zn
Ar
Ar
N N
NN
Zn
Ar
Ar
N N
NN
Zn
Ar
Ar
N
N
Pt Ru Pt
Ph2P
PPh2
PPh2
Ph2PN N
L
L
L
L
1,3-butadiyne linked porphrin porphyrin tape oligo phenylene ethynylene (OPE)
metallopolyyne
N N
NN
Zn
Ar
Ar
N
N N
NN
Zn
Ar
Ar
N N
NN
Zn
Ar
Ar
N N
NN
Zn
Ar
Ar
N
N
Pt Ru Pt
Ph2P
PPh2
PPh2
Ph2PN N
L
L
L
L
1,3-butadiyne linked porphrin porphyrin tape oligo phenylene ethynylene (OPE)
metallopolyyne
Simple 1-d carbon chain = oligoynes
Anchors versus linkers:
Oligoynes
Examples with N=4 carbon
atoms in the chain
(ie n=2 triple bonds)
Amine
CN
Pyridine
Thiol
DHBT
Unfortunately oligoynes are
explosive, so cap the ends
M. Santiago, I. Grace,M. Bryce,
C. Wang, R. Jitchati, A. Batsanov,
S. Higgins, C.J. Lambert,
and R. Nichols,
JACS, S132 9157 (2010)
dihydrobenzo[b]-thiophenyl (DHBT)
Comparison with experiment
Pyridine
thiol
Amine
CN
DHBT
Lo
g G
/G0
Slopes = 0.1 – 0.3 per angstrom
Si-based single-molecule
electronics
8.5 nm SiO2 layer
Si (111)
Polysilicon
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(A)(B)
Gap (~10nm)
Source
Drain Gate
Tunnel Barrier Receptor
Molecular Backbone
I-V characteristics
0 2 4 6
Voltage (V)
0
0.002
0.004
0.006
0.008
0.01
Curr
ent
(nA
)
280K
Measurements in the
absence of molecules
(low leakage currents)
Measurements in the
presence of molecules
Ashwell, et al ACS Nano 4, 7401 (2010)
Also : Angew. Chemie, 50, 8722 (2011)
Molecular wires used in silicon devices
In situ reaction of an amino-terminated molecular linker with
4-ethynylbenzaldehyde electrode-grafted molecules on
opposite sides of the nanogap
Functional units
Mach-Zehnder interferometers
N
N Zn
Ar
Ar
N
N
N
N
ZnAr
N
N
N
N
Zn
Ar
ArN
N
N
N
Zn
Ar
ArN
N
N
N
ZnAr
N
N
N
NZn
Ar
Ar
N
N
NN
N
N N
NS
S
Shielding units
Single-molecule sensing
Phys. Rev. Lett. 102, 086801 (2009)
Simulation of break-junctions Wenjing Hong, David Zsolt Manrique, Pavel Moreno García, Murat Gulcur, Artem Mishchenko,
Colin Lambert, Martin R. Bryce, and Thomas Wandlowski JACS 134, 2292 (2011)
Calculation of pulling curves Classical MD followed by DFT relaxation at each step.
(Morse potential between gold and anchor atom S)
Hunting for Fano resonances and
signatures of room-temperaure
quantum interference R= CH3(CH2)5O T. Wandlowski, V. Kaliginedi, G.P. Moreno; H. Valkenie, W. Hong, V. García-Suárez, P.
Buiter, J. Otten, J. Hummelen and C.J. Lambert, JACS 134 5262 (2012)
Comparison with experiment
The Fano resonance in more
detail
Removal of Fano resonance by
protonation H attached to O
ie O replaced by OH
Geometric control of Fano
resonances
PRB 79, 033405 2009
2
21
2
21
)ΓΓ(εE
Γ4ΓT
1T ε,EFor
4Γ)(
4ΓT,ΓΓΓWhen
22
2
21
E
Breit-Wigner resonances: a reminder
Width Г
Peak position ε
Typical effect of varying a thiol-
gold contact gap
Control of Breit-Wigner
resonances via ring rotation
Transmission coefficient for various
rotation angles between rings
mole
cule
angle
2 0
3 15
4 30
5 46
6 52
7 62
8 88
Control of ring rotations
Experiment; Colombia group: Nature 442, 904 (2006) Theory: Lancaster group, J. Phys.
Cond. Matt. 20, 022203 (2008)
Fano versus Breit-Wigner resonances
ΦHΨ 1
1Γ 2Γ
22)1
2
1
*
21
Γ(ΓεE
εE
Γ4ΓT
side group with eigenvalue ε1
backbone state, with a resonant energy ε Φ
Rotate side group with respect to wire backbone
Phys. Rev. B 74, 193306 (2006)
Control of the Fano resonances via side-
group rotations
Giant thermopower and figure of merit
induced by Fano resonances PRB 79, 033405 2009
Transmission coefficients for various
twist angles
Giant thermopower and figure of
merit in single-molecule devices PRB 79, 033405 2009
• electrical conductance G,
• thermopower S,
• Peltier coefficient Π,
• thermal conductance κ ,
• ZT=S2GT/κ
Moments of the “probability
distribution P(E)=T(E)[-df(E)/dE]”
-
Thermopower versus twist and
temperature
Figure of merit ZT
Collaborators and real workers
Molecular Synthesis
• M.R. Bryce (Durham)
• H. Anderson (Oxford)
Lancaster theory RAs and
PhDs
• V. Garcia-Suarez (now Oviedo)
• L. Oroszlany (now Budapest)
• I. Grace, S. Bailey, C. Finch, D.
Manrique, R. Sparks, D.
Visontai, T. Pope, K. Guillemot,
C. Peterfalvi
Transport measurements and/or
synthesis
• R. Nichols, S. Higgins (Liverpool)
•T. Wandlowskii (Berne)
•N. Agrait (Madrid)
•G. Ashwell (Bangor)
Theory
• J. Ferrer (Oviedo)
• J. Cserti (Budapest)
• J. Jefferson (QinetiQ)
Summary
• ‘Lego’ of single-molecule electronics: anchors, linkers, functional units, pendant groups, ............
• Fano resonances and quantum interference in a series of OPE-derivatives.
• Giant thermopower and figure of merit in single-molecule devices induced by Fano resonances
Experimental evidence of room temperature Fano resonances and quantum interference Beilstein J. Nanotech. 2011, 2, 699 Nature Nano. 2012, 7, 304; PRL. 2012, 109, 056801; Nano. Lett. 2012, 6, 1643; JACS 2012, 134, 5262;
transport
HS
H
)(
General problem
Eg Landauer
G=2e2/h T(EF)
Electron pumping
via Brouwer
formula
Torques and forces
Low – frequency
transport
Thermoelectrics
Ab initio self-consistent mean-
field transport
Spin and Molecular Electronics in Atomically - Generated Orbital Landscapes
Lancaster transport codes + SIESTA + non-equilibrium Greens functions (zero or finite bias; normal or
superconducting contacts; thermoelectrics; non-co-linear magnetism; NEMS)
Victor
Garcia
Porphyrin-based molecular wires
G. Sedghi, L. J. Esdaile, H. L. Anderson, V. M. García-Suárez, C.J.
Lambert, S. Martin, D. Bethell, S. J. Higgins and R. J. Nichols,
Nature Nano, 6 517 (2011)
Example: Planar trimer
(001) Au, with 7x7=49 atoms per layer. Total 588 atoms for trimer
SZ gold ; DZP molecule
Comparison between experiment
and theory
Nature Nano, 6 517 (2011)