Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Department Seminar
Host: R. Ernstorfer

Monday, January 9, 2017, 11:00 am
All are invited to meet around 10:40 am for a chat with coffee & cookies.
Willstätter House, Faradayweg 10
Dr. Hannes Hübener
Nano-bio Spectroscopy Group, Max Planck Institute for the Structure and Dynamics of Matter, Hamburg
Time-dependent band structures of optically driven solids
I will discuss our recently developed approaches to understanding the electronic structure of solids under pump-probe conditions, in particular, how in the Floquet-limit the concept of a band structure can be extended to time-dependent systems and under which conditions it remains an observable of  photo-electron spectroscopy.  I will show how the calculated pump- 
probe photo-electron spectrum of WSe2 shows non-equilibrium feat-ures that are the fingerprint of a steady-state non-equilibrium phase of the material. Such non-equilibrium systems can exhibit a variety of interesting properties, some of which can be funda-mentally different from their equi-librium properties. In this context, I will discuss the possibility how laser pulses can be used to switch between topological phases in a prototypical 3D Dirac material, Na3Bi, and I will demonstrate how lasers can enhance topological protection against lattice perturb-ations. Finally, I will discuss how the excitation of a coherent phonon mode modifies the photo-electron spectrum by electron-phonon coupling.

Figure: Intersection cones in the Floquet band structure of periodically driven Na3Bi forming Floquet-Weyl points