BDT between Au leads
Víctor García Suárez
Outline
1) Experiment
2) Previous calculations
3) Electronic and transport properties
4) Other experiments and simulations
1) Experiment
Experiment
First transport measurement across a molecular junction
Mechanicaly controllable break junction with gold molecules adsorbed
on the gold wire surface
Conductance ~ 10-4 G0 (up to
0.1 G0, Tsutsui et al. Appl. Phys.
Lett. 89, 163111 (2006))
Reed et al., Science
278, 252 (1997)
I-V characteristics
2) Previous calculations
First theoretical calculation
BDT molecule connected to ideal electrodes
Qualitative agreement between theory and experiment
Current and conductace
Di Ventra et al., Phys.
Rev. Lett. 84, 979 (2000)
Full ab-initio calculation
BDT molecule between Au(111) electrodes
Zero bias and out of equlibrium
LUMO
Xue and Ratner , Phys.
Rev. B 68, 115406 (2003)
HOMO
Transmission
Other calculations
Other coupling configurations
Results did not agree with experiments
Stokbro et al.,
Computational
Materials Science
27, 151 (2003)
Transmission
Correlated electron transport
Quantitative agreement for the conductance but not for the I-V
Delaney and Greer,
Phys. Rev. Lett. 93,
36805 (2004)
3) Electronic and transport properties
First approximation to the transport properties
p*
- Two-level system
Each level represents a sulphur level;
both levels interact across the central
part of the molecule
Transmission obtained by
changing the level coupling
S
S
p
Match to the Ab-initio HOMO
Smeagol results
BDT between Au(001) leads
SZ basis set; 9 atoms per lead; 93 atoms in total; slightlty stretched
Transmission and density of states
Phys. Rev. B 80,
085426 (2009)
Effect of stretching and I-V
BDT between Au(001) under stretching and bias voltage
Under strain the junction becomes asymmetric; qualitative I-V agreement
Phys. Stat. Sol. 7,
2443 (2007)
Effect of
stretching
Effect of bias
Example of calculation
BDT between Au(001) leads with 9 atoms per slice
ABAB stacking; coupling on the hollow position (square); distance of 1.9 Å
from the surface; periodic boundary conditions along the perpendicular
directions; 93 atoms in total
Leads calculation
SystemName
Au
SystemLabel
Au
NumberOfAtoms
18
NumberOfSpecies
1
%block ChemicalSpeciesLabel
1 79 Au
%endblock ChemicalSpeciesLabel
%block PAO.Basis
Au 1
n=6 0 1
5.0
%endblock PAO.Basis
%block Ps.lmax
Au 1
%endblock Ps.lmax
LatticeConstant
1.00 Ang
%block LatticeVectors
6.120 6.120 0.000
6.120 -6.120 0.000
0.000 0.000 4.080
%endblock LatticeVectors
AtomicCoordinatesFormat Ang
%block AtomicCoordinatesAndAtomicSpecies
0.00 0.00 0.00 1 Au 1
...
0.00 6.12 2.04 1 Au 18
%endblock AtomicCoordinatesAndAtomicSpecies
%block kgrid_Monkhorst_Pack
1 0 0 0.0
0 1 0 0.0
0 0 100 0.0
%endblock kgrid_Monkhorst_Pack
xc.functional
GGA
xc.authors
PBE
MeshCutoff
200. Ry
MaxSCFIterations
10000
DM.MixingWeight
0.1
DM.NumberPulay
8
DM.MixSCF1
T
DM.Tolerance
1.d-4
SolutionMethod
diagon
ElectronicTemperature
150 K
SaveElectrostaticPotential T
BuildSuperCell T
InitTransport T
BulkTransport T
BulkLead
LR
DM.UseSaveDM
T
Extended molecule calculation
SystemName
Au.em
SystemLabel
Au.em
NumberOfAtoms
93
NumberOfSpecies
4
%block ChemicalSpeciesLabel
1 1 H
2 6 C
3 16 S
4 79 Au
%endblock ChemicalSpeciesLabel
PAO.EnergyShift 0.02 Ry
%block PAO.BasisSizes
H SZ
C SZ
S SZ
%endblock PAO.BasisSizes
%block PAO.Basis
Au 1
n=6 0 1
5.0
%endblock PAO.Basis
%block Ps.lmax
Au 1
%endblock Ps.lmax
LatticeConstant
1.00 Ang
%block LatticeVectors
6.120 6.120 0.000
6.120 -6.120 0.000
0.000 0.000 27.042
%endblock LatticeVectors
...
EMTransport
T
BuildSuperCell T
InitTransport T
NEnergReal
500
NEnergImCircle
50
NEnergImLine
30
NPoles
10
VInitial
0.d0 eV
VFinal
0.d0 eV
NIVPoints
0
Delta
2.d-4
EnergLowestBound
-8.d0 Ry
NSlices
1
AtomLeftVCte
18
AtomRightVCte
76
TrCoefficients
T
NTransmPoints
800
InitTransmRange
-10.5d0 eV
FinalTransmRange
-0.5d0 eV
PeriodicTransp
T
UseLeadsGF
F
HartreeLeadsLeft
-6.44d0 Ang
HartreeLeadsRight 16.52d0 Ang
HartreeLeadsBottom -16.36013222 eV
DM.UseSaveDM
T
Dependence on the lateral size of the electrodes
Size of the electrodes a a function of the number of atoms per layer:
From 4 to 25 atoms per layer (Au 001)
Dependence on the basis set
Type of basis set on the electrodes and molecule:
From SZ in the molecule or leads to DZP in all atoms
Dependence on the number of lateral k-points
Number of k-points along the perpendicular directions
From the G point to 24 k-points
5) Other experiments and simulations
2D conductance histograms of OPE molecules
Number of measurements as a function of length and conductance
An elliptical zone that moves down as a function of length and another
circular zone for very stretched configurations
Wandlosky et al.
Unpublished (yet)
Simulation of BDT with corrected levels (SAINT)
BDT coupled with different atomic configurations and tilt angles
Results that agree qualitatively and quantitatively with experiments
BDT between Au(111)
surfaces
Rigid shift of levels
Conductance as a function of angle and coupling atom I
Hollow and top configurations
Hollow-hollow (not very probable)
Hollow-top
Conductance as a function of angle and coupling atom II
Top configuration
Top-top
Conductance values
Fin