Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 42: Other Transport Topics

TT 42.10: Talk

Wednesday, March 11, 2026, 12:00–12:15, HSZ/0105

Vibrational Instabilities in Molecular Nanojunctions - The Role of Anharmonic Nuclear Potentials — •Martin Mäck, Samuel Rudge, Riley Preston, and Michael Thoss — Institute of Physics, University of Freiburg

Current-induced vibrational excitation is a key factor determining the stability of molecular nanojunctions. Beyond conventional Joule heating, a different mechanism caused by nonconservative current-induced forces has been reported for models with multiple vibrational modes, leading to vibrational instabilities already at low bias voltages [1].

So far, this mechanism has only been investigated for harmonic nuclear potentials [1,2]. A natural question, is whether this effect can also be observed in more realistic models with anharmonic potentials and if it has a measurable impact on observables such as the dissociation probability of the junction. In this contribution, we apply a mixed quantum-classical approach based on electronic friction and Langevin dynamics [2,3] to different anharmonic model systems, studying the influence of anharmonicity on the reported instability and the dissociation dynamics of the junction. The results show that, in our models, anharmonic nuclear potentials destroy the mechanism leading to vibrational instabilities.
[1] J.-T. Lü, M. Brandbyge, P. Hedegård, T.Todorov, D. Dundas, Phys. Rev. B 85, 245444 (2012)
[2] M. Mäck, M. Thoss, S. Rudge, Phys. Rev. B 112, 075430 (2025)
[3] R. J. Preston and D. S. Kosov, J. Chem. Phys. 158,  224106 (2023)

Keywords: Vibrational instabilities; Mixed quantum-classical dynamics; Langevin dynamics; Molecular nanojunctions