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arXiv · 1609.02474

Thermopower of molecular junctions: Tunneling to hopping crossover in DNA

Roman Korol·Michael Kilgour·Dvira Segal
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Abstract

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 voltage-temperature 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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Roman Korol, Michael Kilgour, Dvira Segal. 2016-09-08. Thermopower of molecular junctions: Tunneling to hopping crossover in DNA. https://doi.org/10.1063/1.4971167

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