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PGI Colloquium: 

Prof. Dr. Mads Brandbyge,
Department of Micro- and Nanotechnology and Center for Nanostructured Graphene,
Technical University of Denmark, Lyngby, Denmark


PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

12 Feb 2016 11:00

Currents in nano-conductors: exciting atomic motion

In the Landauer approach to nanoscale transport the electrons are assumed to bypass a conducting junction ballistically and equilibrate through energy exchange in the electrodes. However, when passing through the junction, the current-carrying electrons has a finite, albeit small, probability to interact with the atomic vibrations (phonons) in the junction leading to local energy and momentum transfer. At low voltage this can be used as a powerful spectroscopic tool for example in the Scanning Tunnelling Microscope (STM).

On the other hand, in the presence of a high current density the current will not only lead to Joule heating: Recently a number of other mechanisms have been pointed out in which the current may excite and influence the atomic motion in nano-junctions, and possibly lead to instabilities and contact disruption. These include energy non-conserving forces (“curl forces”), and forces rooted in the quantum Berry phase of the nonequilibrium electrons (“Berry forces”).
I will motivate our research and present calculations of the effects in atomic, molecular, and graphene-based junctions using methods based on Density Functional Theory and Non-equilibrium Greens functions.


Prof. Dr. Maarten Rolf Wegewijs
Phone: +49 2461 61-4017
Fax: +49 2461 61-2620