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TT: Fachverband Tiefe Temperaturen
TT 42: Other Transport Topics
TT 42.9: Vortrag
Mittwoch, 11. März 2026, 11:45–12:00, HSZ/0105
Negative electronic friction and non-Markovianity in charge transport through molecular nanojunctions — •Riley Preston1, Samuel Rudge1, Daniel Kosov2, and Michael Thoss1 — 1Institute of Physics, University of Freiburg — 2College of Science and Engineering, James Cook University
The electronic friction approach is a popular mixed quantum-classical method for modeling the dynamics of atoms and molecules at metal or semiconductor surfaces. If the electrons are far from equilibrium, such as in molecular nanojunctions at high bias voltages, the electronic friction coefficient can become negative, meaning it acts to amplify the nuclear vibrations in the molecular bridge rather than dampen them, triggering bond rupture and a loss of device functionality. The physicality of negative electronic frictions has long been debated, owing to the hierarchy of underlying assumptions upon which the electronic friction method is built. We investigate the emergence of negative electronic friction in a donor-acceptor model of a molecule in a molecular nanojunction. We observe that negative electronic frictions arise predictably at high bias voltage according to the geometry of the donor and acceptor on the molecular bridge, resulting in large vibrational excitations that are validated by comparison to numerically exact quantum data calculated with the hierarchical equations of motion approach. However, we also show that the same physical conditions that give rise to negative electronic friction are also suggestive of non-Markovian dynamics, challenging the underlying assumptions of the electronic friction approach.
Keywords: Electronic friction; Non-Markovian dynamics; Non-adiabatic dynamics; Nonequilibrium molecular dynamics; Langevin dynamics