Project Details
Projekt
System for time-, spin- and momentu-resolved photoemission with ultrashort X-ray pulses
Subject Area
Condensed Matter Physics
Term
Funded in 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 566157266
In recent years, time-resolved photoelectron spectroscopy with ultrashort X-ray pulses has become one of the most versatile experimental tools for the study of fundamental ultrafast phenomena in condensed matter. It allows, for example, the study of the femtosecond dynamics of optically excited charge and spin carriers in molecular adsorbate systems and quantum materials, or the imaging of transient changes in the spin-dependent band structure of magnetic or topological systems after optical excitation. Even today, such experiments are still very challenging, especially for the investigation of the spin degree of freedom. This is mainly due to the typically low pulse repetition rate (<50 kHz) of the laboratory light sources for ultrashort soft X-ray pulses and the low detection efficiency of the spin detectors commonly used today. Together they limit the achievable data quality (or the required signal-to-noise ratio) and make a reliable interpretation of the experimental results very difficult. These challenges have only recently been overcome thanks to recent innovations in laser technology and the development of new spin detector concepts, known as VLEED detectors. Here we apply for such a 'complete' photoelectron spectroscopy experiment with time, spin, energy and momentum resolution throughout the Brillouin zone, including a tunable laboratory light source for ultrashort pulses in the soft X-ray range between 30 eV and 100 eV. Its main components are a high-power fiber laser system with pulse repetition rates of at least 100 kHz with a downstream nonlinear compression stage for sub-50 fs pulses and an optical parametric amplifier system. Such an overall system allows the simultaneous generation of ultrashort X-ray pulses by higher harmonic generation as well as tunable ultrashort laser radiation for optical excitation of the materials. The second main component is a photoelectron spectroscopy system with a hemispherical electron analyser with large angular acceptance (±30°) for two orthogonal momentum directions of the electrons in fixed experimental geometry and a highly efficient vectorial spin detector to determine the spin polarisation of the photoelectrons in all three spatial directions. This novel system for ultrafast photoemission experiments will provide unique insights into the full spin-dependent band structure dynamics of low-dimensional quantum materials and magnetic and topological systems on the time scale of a few fs, and thus form the basis for coherent control protocols on the shortest time and smallest length scales.
DFG Programme
Major Research Instrumentation
Major Instrumentation
Anlage für zeit-, spin- und impulsaufgelöste Photoemission mit ultrakurzen Röntgenpulsen
Instrumentation Group
1780 Photoelektronenspektrometer (UPS und XPS)
Applicant Institution
Universität Augsburg
