SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 60: Quantum Dots, Quantum Wires, Point Contacts

TT 60.5: Vortrag

Donnerstag, 30. März 2023, 18:15–18:30, HSZ 03

Vibrational instabilities arising from non-conservative current-induced forces in nanosystems: A comparison of quantum and semi-classical approaches — •Samuel Rudge, Christoph Kaspar, and Michael Thoss — Institute of Physics, University of Freiburg, Germany

Understanding the vibrational dynamics of molecular junctions is of paramount importance to creating junctions that are mechanically stable. In systems with more than one vibrational degree of freedom, instabilities can arise due to non-conservative current-induced forces, an effect that can occur at lower voltages than the well-understood mechanism of current-induced heating [1].

In recent years, such non-conservative forces have been largely explored with semi-classical Langevin-type equations for the vibrational degrees of freedom, where the electronic friction tensor and average electronic force can be analyzed directly [1]. In this work, however, we employ both a semi-classical Langevin equation as well as a quantum master equation approach to explore instabilities in a model system with two electronic levels and two vibrational modes. Both approaches derive from the numerically exact hierarchical equations of motion (HEOM) method [2], and the resulting analysis is able to show in which regimes such semi-classical treatments can be used.

[1] J. T. Lü et al., Phys. Rev. B 85, 245444 (2012)
[2] S.L. Rudge, Y. Ke, and M. Thoss, arXiv:2211.14215 (2022)