Thermoelectric effect and its dependence on molecular length and sequence in single DNA molecules

Abstract

Studying the thermoelectric effect in DNA is important for unravelling charge transport mechanisms and for developing relevant applications of DNA molecules. Here we report a study of the thermoelectric effect in single DNA molecules. By varying the molecular length and sequence, we tune the charge transport in DNA to either a hopping- or tunnelling-dominated regimes. The thermoelectric effect is small and insensitive to the molecular length in the hopping regime. In contrast, the thermoelectric effect is large and sensitive to the length in the tunnelling regime. These findings indicate that one may control the thermoelectric effect in DNA by varying its sequence and length. We describe the experimental results in terms of hopping and tunnelling charge transport models.

Thermopower of molecular junctions: Tunneling to hopping crossover in DNA

“…Regarding the experiment reported in Ref. 12 , our VTP simulations support the identification of the different transport limits. We also suggest measuring the temperature dependence of G and S, around room temperature, for this family of DNA sequences (Table I).…”

“…We examine the reported results of Ref. 12 : The tunneling value is S T (n = 10) = 6 µV/K, while S H (n = 16) = 2 µV/K. The ratio between these values reasonably satisfy theoretical predictions.…”

“…(ii) Understand the transition between the different mechanisms based on numerical simulations. (iii) Use simulations to explore the recently reported tunneling-to-hooping crossover in DNA molecules as manifested in the thermopower 12 .…”

Controlling charge transport mechanisms in molecular junctions: Distilling thermally induced hopping from coherent-resonant conduction

“…The competition between superexchange tunneling and thermally-induced hopping transport has been the subject of many investigations, examined in different types of molecules, such as conjugated organic molecules [4][5][6][7][8][9][10][11] and biomolecules [12][13][14][15][16][17][18][19][20] . Observations of nearly lengthindependent conduction [21][22][23] , or temperature dependent conduction which can be associated to the thermal broadening of the Fermi functions 21,[24][25][26] , point to phasecoherent resonant transmission as the dominant transport mechanism.…”

“…However, if one's objective is to learn about electron-vibration interaction effects (inelastic scattering, heat generation, phonon transport, phonon damping, phonon cooling), that are intrinsic to the molecular entity, one should aim to reduce the "irrelevant" ballistic contribution, so as to observe signatures of electron-nuclei interaction effects, in particular, the tunneling-to-hopping crossover. This challenge is especially relevant to relatively short molecular junctions in which the three mechanisms discussed above can show up simultaneously, to confound the identification of the dominant transport mechanism [4][5][6][7][8][9]11,16,17,21,22,24,25 . In this paper, we propose a simple design for molecular junctions, with the objective to suppress phasecoherent resonant conduction.…”