Ultrafast Broadband Spectroscopy on Correlated Materials

This thesis deals with femtosecond broadband spectroscopy in the visible regime, which is used to study strongly correlated electron systems. The materials that were studied are high-temperature cuprate superconductors of various dopings and the charge-density wave material tantalum disulfide. Central results comprise the coherent excitation and the detection of a charge fluctuation of the superconducting condensate in optimally doped lanthanum strontium cuprate, the quantification of the electron-phonon coupling in lanthanum cuprate, including the description of a method to directly extract matrix elements from the time-resolved experiments, the observation of spectroscopic evidence for paired electrons far above the superconducting transition temperature in neodymium barium cuprate, and a detailed study of coherent phonons associated with the charge ordering in tantalum disulfide.

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