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PGI-1 Talk: Dr. Marco Battiato

Boltzmann treatment of out-of-equilibrium dynamics

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20 Sep 2017 11:30
venue
PGI Lecture Hall

Institute of Solid State Physics, Vienna University of Technology (TU Wien)

Abstract:

Recent years have seen a surge in the interest in ultrafast dynamics in solids. This is also due to the discovery of a number of effects that arise from the non-trivial interplay of out-of-equlibrium electron equilibration and transport in band structures with specific characteristics of real band structures and heterostructures, and the formation and propagation of electromagnetic fields. These new discoveries could pave the way to a fully sub-picosecond spintronics, which would be thousand times faster than current electronics.

A key example was the prediction and subsequent verification of superdiffusive spin transport as one of the drivers of the ultrafast demagnetisation. That discovery laid the ground to the field of ultrafast spin transport. This opened a rich playground where effects such as hot-carrier-driven demagnetisation, the ultrafast increase of magnetisation, and the production of THz radiation were predicted and observed. Recently the ultrafast injection of highly spin polarised current pulses into semiconductors has been predicted. All these effects can be explained and understood only by describing the electronic motion in real band structures and real multilayers, with explicit coupling to the dynamics of electromagnetic fields. The Boltzmann approach is the best way to tackle such an ambitious task, which is way beyond the reach of other quantum mechanical methods.

I will first show how, in spite of the common feeling, the so unfortunately called “semiclassical approximation” is instead extremely precise and can be seen as an extremely clever transform of the Schrödinger equation, and how its reduction to the Boltzmann equation is acceptable for ultrafast incoherent dynamics. I will then describe the main challenges in solving numerically the Boltzmann equation, namely the scattering term, the progress we have done so far, and the problems we will be able to tackle in the near future.

Contact

Prof. Dr. Stefan Blügel
Phone: +49 2461 61-4249
Fax: +49 2461 61-2850
email: s.bluegel@fz-juelich.de

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