Thermopower of molecular junctions: Tunneling to hopping crossover in DNA
Abstract
We study the electrical conductance and the thermopower 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 and 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 B\"uttiker'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).
Keywords
Cite
@article{arxiv.1609.02474,
title = {Thermopower of molecular junctions: Tunneling to hopping crossover in DNA},
author = {Roman Korol and Michael Kilgour and Dvira Segal},
journal= {arXiv preprint arXiv:1609.02474},
year = {2017}
}