Department of Physical Chemistry, Fritz Haber Institute of the MPG 

Lattice Dynamics Group

Alex Paarmann
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Welcome to the web site of the Lattice Dynamics group! 

Our newly established group is currently setting up experiments to study the ultrafast evolution of solids after resonant excitation of the lattice. The aim of these studies is to understand the role of specific lattice modes in determining the microscopic and macroscopic properties of the solid, as well as exploring the possibilities to control the material properties transiently via mode-selective lattice excitation.

The lattice excitation is realized with two complementary techniques: (i) direct mid-infrared and (ii) impulsive Raman excitation. For mid-infrared excitation, we use the ps-pulses generated by the recently commissioned FHI Free Electron Laser (FEL). Impulsive Raman excitation is achieved with tunable femtosecond laser pulses in the visible to ultraviolet region from a table top fs laser system. We use a wide range of optical and electrical probes to follow the response of the sample to the lattice excitation.

Making use of the special pulse structure of the FHI FEL, we develop new spectroscopic techniques to access dynamics on mixed ps/ns timescales in the sample response by combining the ps pump-probe method with ns-resolved real-time detection within the FEL macropulses