# Berlin 2018 – wissenschaftliches Programm

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# SYSD: Symposium SKM Dissertation-Prize 2018

## SYSD 1: SKM Dissertation-Prize 2018

### SYSD 1.5: Hauptvortrag

### Montag, 12. März 2018, 12:20–12:40, HE 101

**Electron-phonon interactions beyond the two-temperature approximation** — •Lutz Waldecker — Stanford University, Stanford, CA 94305, USA — Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Deutschland

The coupling between electrons and phonons is central to solid state physics as it determines fundamental effects ranging from transport phenomena to many-body effects like superconductivity. Despite the complexity of the problem on the microscopic level, the energy exchange between electronic and vibrational degrees of freedom is typically approximated by simple models assuming thermal distribution functions of the populations in both subsystems.

In this talk, I will present measurements of the electron-phonon coupling strength in simple metals, semimetals and semiconductors employing femtosecond electron diffraction. This technique allows following the thermal relaxation dynamics after photoexcitation of a material's electrons by measurement of its phonon populations with time- and momentum-resolution, therefore providing a picture beyond ensemble averages near- as well as far out of equilibrium. I will discuss the limits of the two-temperature model for the interpretation of these measurements and present easy to solve models that can significantly improve the microscopic description of electron-phonon scattering.