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TT: Fachverband Tiefe Temperaturen

TT 47: Fluctuations, Noise and Other Transport Topics (joint session TT/DY)

TT 47.12: Vortrag

Donnerstag, 20. März 2025, 18:00–18:15, H31

Vibrational instabilities in molecular nanojunctions: A mixed quantum-classical analysis — •Martin Mäck, Samuel Rudge, Riley Preston, and Michael Thoss — Institute of Physics, University of Freiburg

Understanding the current-induced vibrational dynamics in molecular nanojunctions is critical for gaining insight into the stability of such systems. While it is well known that Joule at higher bias voltages plays an important role for the stability of the nanojunction, a different mechanism caused by current-induced nonconservative forces has been reported to cause vibrational instabilities already at much lower voltages [1].

In this contribution, we apply a mixed quantum-classical approach based on electronic friction and Langevin dynamics [2,3] to a model system for which vibrational instabilities have previously been reported. Such a mixed quantum-classical description has the benefit of giving valuable insight into the electronic forces acting on the molecular vibrations. We analyze the possible occurrence of vibrational instabilities and compare our results to previous approaches, which were limited to small amplitude motion of the vibrational degrees of freedom [1].
[1] J.-T.Lü, M.Brandbyge, P.Hedegård, Nano Lett. 10, 1657 (2010).
[2] S.L.Rudge, C.Kaspar, R.L.Grether, S.Wolf, G.Stock, M.Thoss, J.Chem. Phys.160, 184106 (2024).
[3] R.J.Preston, D.S.Kosov, J.Chem.Phys.158,  224106 (2023).

Keywords: mixed quantum-classical dynamics; electronic friction; vibrational instabilities; Langevin dynamics