Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 19: Poster 2: Biomolecules, Cold Molecules, Experimental Techniques, Various Topics

MO 19.16: Poster

Wednesday, March 20, 2013, 16:00–18:30, Empore Lichthof

Sequential transport through molecules with rapidly fluctuating bridges — •Bogdan Popescu¹, Benjamin Woiczikowski², Marcus Elstner², and Ulrich Kleinekathoefer¹ — ¹Jacobs University Bremen — ²Karlsruhe Institute of Technology

Charge transport through molecular junctions is a key subject in nowadays nanoscale physics. In many studies the molecule is placed in an aquateus environment, subject to solvent fluctuations, which lead to incoherent effects and influence the transport significantly. We model the molecular junction as a tight-binding chain coupled to fermionic leads. As an example we choose a double-stranded DNA heptamer with base sequence poly(dG)-poly(dC). By classical equilibrium MD simulations and quantum chemistry calculations, one obtains time series of on-site energies and inter-site couplings. These trajectories are then employed to compute the electric current through the system. Our contribution consists of using a recently developed propagation scheme [2] based on NEGF, which renders the current through the device as a function of time, and comparing its outcomes with the snapshot-averaged Landauer approach. We find that for scenarios with rapidly fluctuating system parameters the dominant transfer mechanism is sequential transport. In addition, the Landauer method which accounts only for the coherent transfer of electrons is shown not to be a proper method of choice for such scenarios.
[1] P. B. Woiczikowski et. al., J. Chem. Phys. 130, 215104 (2009).
A. Croy and U. Saalmann, Phys. Rev. B 80, 245311 (2009).
B. Popescu et. al., Phys. Rev. Lett 109, 176802 (2012).