A time domain perspective on electron-boson coupling in superconducting materials
10:30 - 12:00
University of Duisburg-Essen, Faculty of Physics
CFEL (Bldg. 99)
Seminar Room IV, O1.111
Experiments in the time domain allow to determine the electron-boson coupling strength by analyzing the second moment of the Eliashberg function α2∙F(ω) using the relaxation time constant of thermalized, hot electrons after optical excitation.  While this approach works well for conventional superconducting materials, it is under discussion for unconventional superconductors due to competing electron and boson dynamics on similar time scales. [2,3]
It is therefore desired to identify well defined bosonic or electronic
signatures in time-resolved spectroscopy. In this talk results of
femtosecond time- and angle-resolved photoemission on cuprate and
Fe-based superconductors will be presented. Experimentally observed,
well defined boson signatures [4,5], which originate from restrictions
in the relaxation phase space  will be discussed. We show that
coupling to specific bosonic excitations, which were identified by
ultrafast electron diffraction for the case of Bi-2212 to consist of
in-plane lattice vibration,  inhibits thermalization of the excited
electron distribution. Such microscopic insight provides opportunities
to analyze the electron-boson coupling directly, without the assumption
of a thermalized electron distribution.
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