<i>Ab initio</i>study of the thermopower of biphenyl-based single-molecule junctions

Bürkle, Marius; Zotti, Linda A.; Viljas, J. K.; Vonlanthen, David; Mishchenko, Artem; Wandlowski, Thomas; Mayor, Marcel; Schön, Gerd; Pauly, Fabian

doi:10.1103/physrevb.86.115304

Cited by 45 publications

(57 citation statements)

References 45 publications

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“…[26]. Introducing the substituents leads to a shift of the molecular orbital energies relative to E F [52]. For the electron-donating substituents NH 2 and OH, the molecular frontier orbital energies increase due to the increased Coulomb repulsion in the conjugated π -electron system of the benzene rings.…”

Section: Resultsmentioning

confidence: 99%

First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

et al. 2015

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Here we present a theoretical study of the thermoelectric transport through [2,2]paracyclophane-based singlemolecule junctions. Combining electronic and vibrational structures, obtained from density functional theory (DFT), with nonequilibrium Green's function techniques allows us to treat both electronic and phononic transport properties at a first-principles level. For the electronic part, we include an approximate self-energy correction, based on the DFT+ approach. This enables us to make a reliable prediction of all linear response transport coefficients entering the thermoelectric figure of merit ZT . Paracyclophane derivatives offer a great flexibility in tuning their chemical properties by attaching different functional groups. We show that, for the specific molecule, the functional groups mainly influence the thermopower, allowing us to tune its sign and absolute value. We predict that the functionalization of the bare paracyclophane leads to a largely enhanced electronic contribution Z el T to the figure of merit. Nevertheless, the high phononic contribution to the thermal conductance strongly suppresses ZT . Our work demonstrates the importance to include the phonon thermal conductance for any realistic estimate of the ZT for off-resonant molecular transport junctions. In addition, it shows the possibility of a chemical tuning of the thermoelectric properties for a series of available molecules, leading to equally performing hole-and electron-conducting junctions based on the same molecular framework.

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Section: Resultsmentioning

confidence: 99%

First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

et al. 2015

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“…This discrepancy with the experiments may be due to a partly incorrect description of the alignment of the LUMO with the gold Fermi energy, which is a known deficiency of DFT-based approaches. 49,50 Let us also mention that for the ideal junctions in Fig. 1(a) we obtain a thermopower of −19.37 μV/K for the hollow geometry and a value of −91.62 μV/K for the top one.…”

Section: Conductance and Thermopower Of Gold-c 60 -Gold Junctionsmentioning

confidence: 99%

Theoretical study of the charge transport through C60-based single-molecule junctions

et al. 2012

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We present a theoretical study of the conductance and thermopower of single-molecule junctions based on C 60 and C 60 -terminated molecules. We first analyze the transport properties of gold-C 60 -gold junctions and show that these junctions can be highly conductive (with conductances above 0.1G 0 , where G 0 = 2e 2 /h is the quantum of conductance). Moreover, we find that the thermopower in these junctions is negative due to the fact that the lowest unoccupied molecular orbital dominates the charge transport, and its magnitude can reach several tens of microvolts per kelvin, depending on the contact geometry. On the other hand, we study the suitability of C 60 as an anchoring group in single-molecule junctions. For this purpose, we analyze the transport through several dumbbell derivatives using C 60 as anchors, and we compare the results with those obtained with thiol and amine groups. Our results show that the conductance of C 60 -terminated molecules is rather sensitive to the binding geometry. Moreover, the conductance of the molecules is typically reduced by the presence of the C 60 anchors, which in turn makes the junctions more sensitive to the functionalization of the molecular core with appropriate side groups.

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“…Focusing on works reporting on both G and S, we note that most computational studies of linear-response transport coefficients in single molecules are limited to the coherent limit 23 , using the Landauer formula with parameters derived from first principle calculations [24][25][26][27][28][29][30][31][32][33][34] , or other coherent-transport approaches 35 . Effects of vibrations on the thermopower were assessed using scattering approaches 36,37 , or perturbatively using non-equilibrium Green's function (NEGF) [38][39][40][41][42][43] or quantum master equation (QME) methods [42][43][44][45][46] .…”

Section: Introductionmentioning

confidence: 99%

Thermopower of molecular junctions: Tunneling to hopping crossover in DNA

Korol

Kilgour

Segal

2016

The Journal of Chemical Physics

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We study the electrical conductance G and the thermopower S of single-molecule junctions, and reveal signatures of different transport mechanisms: off-resonant tunneling, on-resonant coherent (ballistic) motion, and multi-step hopping. These mechanisms are identified by studying the behavior of G and S while varying molecular length and temperature. Based on a simple one-dimensional model for molecular junctions, we derive approximate expressions for the thermopower in these different regimes. Analytical results are compared to numerical simulations, performed using a variant of Büttiker's probe technique, the so-called voltagetemperature probe, which allows us to phenomenologically introduce environmentally-induced elastic and inelastic electron scattering effects, while applying both voltage and temperature biases across the junction. We further simulate the thermopower of GC-rich DNA molecules with mediating A:T blocks, and manifest the tunneling-to-hopping crossover in both the electrical conductance and the thermopower, in accord with measurements by Y. Li et al., Nature Comm. 7, 11294 (2016).

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Ab initiostudy of the thermopower of biphenyl-based single-molecule junctions

Cited by 45 publications

References 45 publications

First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

Theoretical study of the charge transport through C60-based single-molecule junctions

Thermopower of molecular junctions: Tunneling to hopping crossover in DNA

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