Two-photon photoemission uses a combination of optical pump-probe techniques and angle-resolved photoelectron spectroscopy to study ultrafast electronic processes at surfaces with a time resolution of femtoseconds. For a brief description of the method, see our 2PPE tutorial.
At the Lehrstuhl für Festkörperphysik, we hold extensive optical and ultrahigh vacuum (UHV) equipment for 2PPE experiments. The facilities include three individual setups, each equipped with a femtosecond Ti:sapphire laser system, optical characterization by spectrometers and autocorrelators, and an UHV chamber holding an electron analyzer. Each UHV chamber is also equipped with LEED optics, evaporators, an ion gun, sample heating, and a cleaving mechanism to prepare atomically well-defined surfaces. Samples can be cooled to liqud nitrogen temperature for experiments. In addition to LEED, samples are characterized and complemetary studies on valence band and core electronic structure are performed using UV photoemission and x-ray photoemission. The flexibility of the experimental facilities benefits significantly from in-house mechanical and electronic workshops, which find costumized solutions to the requirements of the individual experiments.