Dr. Ralph Ernstorfer

Graz Advanced School of Science
PHYSICS COLLOQUIUM OF THE UNIVERSITY OF GRAZ AND
THE GRAZ UNIVERSITY OF TECHNOLOGY
Dr. Ralph Ernstorfer
Max Planck Research Group for Structural & Electronic Surface Dynamics
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
http://w0.rz-berlin.mpg.de/pc/ernstorfer
Electronic and Structural Dynamics in Solids: A Momentum-Resolved View
on Microscopic Coupling and Correlation Phenomena
Abstract:
The coupling and mutual dependence of electronic and vibrational degrees of freedom is at the heart of
microscopic as well as macroscopic phenomena in condensed matter. Ultrafast pump-probe techniques
provide experimental access to these coupling and correlation effects by revealing the microscopic
response to specific excitation of a material. In particular, we employ time- and angle-resolved
photoelectron spectroscopy (trARPES) and femtosecond electron diffraction (FED) [1] and imaging [2] in
order to obtain a momentum-resolved view on the dynamics of electrons and phonons.
I will discuss electron-lattice interaction and electron dynamics in two classes of materials. First, the
electron-phonon coupling in the free-electron metal aluminium is revisited and quantitatively
investigated with FED and first-principle calculations. Our results challenge the validity of the twotemperature approximation and we propose
a refined non-thermal lattice model [3].
Second, I will discuss ultrafast electron and
phonon dynamics in the semiconducting
transition metal dichalcogenide WSe2.
TrARPES with fs XUV pulses reveals the
evolution of spin- and pseudospin-polarized
excited states and allows for mapping of the
conduction band structure in the entire Brillouin zone. The complementary momentum-resolved
dynamics of phonons in this material is studied by FED.
[1]
[2]
[3]
[4]
L. Waldecker et al., J. Appl. Phys. 117, 044903 (2015).
M. Müller et al., Nature Communications 5, 5292 (2014).
M. Müller et al., ACS Photonics 3, 611 (2016).
L. Waldecker et al., Phys. Rev. X 6, 021003 (2016).
R. Bertoni et al., arXiv:1606.03218.
Termin:
Ort:
Dienstag, 21.6.2016, 17.00 Uhr KFU Graz
KFU Graz, Universitätsplatz 5, Hörsaal 05.01,
Meet-the-speaker ab 16.30 Uhr, Bibliothek des FB Experimentalphysik, 1. Stock, ZiNr.: 122
Gastgeber:
Univ.-Prof. Dr. Martin Sterrer – Inst. f. Physik – Surface Science
For a regularly updated colloquium program see: http://www.if.tugraz.at/colloquium.html

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