bdt between au leads víctor garcía suárez. outline 1) experiment 2) previous calculations 3)...
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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
Reed et al., Science 278, 252 (1997)
I-V characteristics
Conductance ~ 10-4 G0 (up to 0.1 G0, Tsutsui et al. Appl. Phys. Lett. 89, 163111 (2006))
2) Previous calculations
First theoretical calculation
BDT molecule connected to ideal electrodes
Qualitative agreement between theory and experiment
Current and conductaceDi 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
Xue and Ratner , Phys. Rev. B 68, 115406 (2003)
LUMO
HOMO
Transmission
Other calculations
Other coupling configurations
Results did not agree with experiments
Stokbro et al., Computational Materials Science 27, 151 (2003)
Delaney and Greer, Phys. Rev. Lett. 93, 36805 (2004)
Transmission
Correlated electron transport
Quantitative agreement for the conductance but not for the I-V
3) Electronic and transport properties
First approximation to the transport properties
- Two-level system
Each level represents a sulphur level; both levels interact across the central part of the molecule
S S
Transmission obtained by changing the level coupling
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 statesPhys. 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 AuSystemLabel AuNumberOfAtoms 18NumberOfSpecies 1%block ChemicalSpeciesLabel 1 79 Au%endblock ChemicalSpeciesLabel%block PAO.BasisAu 1 n=6 0 1 5.0%endblock PAO.Basis%block Ps.lmax Au 1%endblock Ps.lmaxLatticeConstant 1.00 Ang%block LatticeVectors 6.120 6.120 0.000 6.120 -6.120 0.000 0.000 0.000 4.080%endblock LatticeVectorsAtomicCoordinatesFormat 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_Packxc.functional GGAxc.authors PBEMeshCutoff 200. RyMaxSCFIterations 10000DM.MixingWeight 0.1DM.NumberPulay 8DM.MixSCF1 TDM.Tolerance 1.d-4SolutionMethod diagonElectronicTemperature 150 KSaveElectrostaticPotential TBuildSuperCell TInitTransport TBulkTransport TBulkLead LRDM.UseSaveDM T
Extended molecule calculationSystemName Au.emSystemLabel Au.emNumberOfAtoms 93NumberOfSpecies 4%block ChemicalSpeciesLabel 1 1 H 2 6 C 3 16 S 4 79 Au%endblock ChemicalSpeciesLabelPAO.EnergyShift 0.02 Ry%block PAO.BasisSizes H SZ C SZ S SZ%endblock PAO.BasisSizes%block PAO.BasisAu 1 n=6 0 1 5.0%endblock PAO.Basis%block Ps.lmax Au 1%endblock Ps.lmaxLatticeConstant 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 TBuildSuperCell TInitTransport TNEnergReal 500NEnergImCircle 50NEnergImLine 30NPoles 10VInitial 0.d0 eVVFinal 0.d0 eVNIVPoints 0Delta 2.d-4EnergLowestBound -8.d0 RyNSlices 1AtomLeftVCte 18AtomRightVCte 76TrCoefficients TNTransmPoints 800InitTransmRange -10.5d0 eVFinalTransmRange -0.5d0 eVPeriodicTransp TUseLeadsGF FHartreeLeadsLeft -6.44d0 AngHartreeLeadsRight 16.52d0 AngHartreeLeadsBottom -16.36013222 eVDM.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 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-top
Conductance values
Top configuration
Fin