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TT: Fachverband Tiefe Temperaturen

TT 99: Poster Session: Transport

TT 99.7: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Bias-dependent forces in single-molecule junctions — •Susanne Leitherer¹, Jonathan Brand², Nick P. Rübner¹, Nicolas Neel², Jörg Kröger², and Mads Brandbyge¹ — ¹Department of Micro- and Nanotechnology, Technical University of Denmark — ²Institut für Physik, Technische Universität Ilmenau

We study the forces on single-molecule junctions formed by C₆₀-terminated Cu tips and C₆₀ molecules adsorbed on Cu(111) employing first principles electronic structure and transport calculations based on density functional theory combined with non-equilibrium Greens functions (DFT-NEGF). The C₆₀-C₆₀ bond force evaluated at different distances and voltages shows an asymmetric dependence on the bias polarity. This asymmetry can be related to bias-dependent electrostatic forces between the charge densities localized at the molecules, and also indicates the effect of current-induced forces. We discuss various ways to rationalize these forces in terms of transmission eigenchannels, charge redistribution, overlap populations and bond-currents. Our simulations support the results of scanning tunneling microscopy studies on the junctions using bias-dependent force spectroscopy, which cannot be explained without accounting for the non-equilibrium forces in single-molecule junctions.