Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 66: Ultrafast Dynamics of Light-Driven Systems

TT 66.4: Vortrag

Freitag, 5. April 2019, 10:30–10:45, H2

Ultrafast dynamics of superconductors: Cooper-pair Dephasing or Thermalization? — •Christopher Stahl and Martin Eckstein — Lehrstuhl für Theoretische Festkörperphysik, FAU Erlangen-Nürnberg, Deutschland

We investigate the ultrafast dynamics of superconductivity in a BCS model. The reduction of the gap after different excitation protocols, which has been observed in various theoretical and experiential studies, may in principle be due to dephasing of the pair correlations at individual momenta, or due to thermalization to a hot electron state. While in time-dependent BCS theory it is clear that the gap would only dephase, we show, using non-equilibrium dynamical mean-field theory, that dephasing and thermalization can be clearly distinguished on short times even beyond mean-field theory. Furthermore we propose an experimental protocol to obtain the pair correlations at individual momenta and thus distinguish the two scenarios. This scheme, which is based on a measurement of the statistical variance of the number of photoelectrons in each momentum state in time-resolved pump-probe photoemission spectroscopy, can more generally provide a way to obtain two-particle quantities in a time-resolved fashion. The technique requires only a small bandwidth of the probe pulse in frequency space and can therefore yield a high time-resolution.