Charge transport and current-induced forces in nanostructures: Reduced approaches based on Langevin dynamics and hierarchical quantum master equations

• Applicant: Professor Dr. Michael Thoss
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431945604

Electrical transport in nanostructures such as atomic wires, molecular junctions or graphene is often accompanied by strong interaction between electrons and mechanical degrees of freedom, such as local vibrational modes. At higher bias voltages, i.e., far from thermal equilibrium, this interaction gives rise to nonconservative current-induced forces and unique dissipative phenomena related to electronic friction, which can have significant implications. For example, nonconservative current-induced forces can cause high excitation of local vibrational modes and the electronic friction, which the vibrational degrees of freedom experience due to coupling to the electrons, can assume negative values. These effects may cause mechanical instabilities of the nanostructures. Therefore, a comprehensive analysis and understanding of the underlying mechanisms are crucial for the further advancement of nanoelectronic systems. To achieve this objective, the current project, which is part of the Research Unit „Reducing complexity of nonequilibrium systems“, focuses on the development of consistent and accurate theoretical methods to study charge transport and current-induced mechanical motion of nanosystems out of equilibrium. Several strategies will be pursued, which all employ the concept of a reduced description of the overall complex problem. These strategies include mixed quantum-classical methods, such as advanced Langevin- and Ehrenfest-type approaches, as well as fully quantum mechanical theories of electronic friction. The application of these methods to charge transport in atomic nanowires will provide important insight into basic mechanisms and characteristics of current-induced forces and electronic friction. Furthermore, current-driven molecular rotors will be investigated as a specific example of molecular motors.

• DFG Programme: Research Units
• Subproject of: FOR 5099: Reducing complexity of nonequilibrium systems
• Co-Investigators: Professor Dr. Heinz-Peter Breuer; Professor Dr. Gerhard Stock