Generation and spectroscopy of ultrashort two-dimensional electrical currents at metal and semiconductor surfaces

• Applicant: Privatdozent Dr. Jens Güdde
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2012 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 195902694

The goal of this project is the optical excitation and time-resolved detection of ultrashort electrical currents on well defined solid state surfaces in order to investigate the microscopic scattering processes of optical excited electrons and their impact on charge transport. The focus is in particular on the investigation of elastic scattering processes which are responsible for the decay of currents due to a redistribution of excited electrons in momentum space. The detection of these currents by means of time- energy- and momentum-resolved photoelectron spectroscopy will be realized by employing an electron time-of-flight spectrometer, which has been developed and tested in the first funding period and which is capable to measure the energy and momentum of photoelectrons in both directions of the two-dimensional surface band structure. In the continuation of the project, this time-of-flight spectrometer shall be used for the time-resolved observation of the photocurrent dynamics in the topological protected surface state of Sb2Te3 in order to investigate the impact of the spin texture of the surface state and the therewith implicated prohibition of backscattering on the momentum dynamics. In a second step, the simultaneously observable range in momentum space shall be increased up to a full Brillouin zone by combining the time-of-flight spectrometer with a high harmonics laser source that we have recently developed in our group. This setup shall be used for the investigation of the charge transfer dynamics between different points of the surface Brillouin zone of transition metal dichalconides following optical excitation in the visible range. By using circular polarized optical excitations, it shall be proved to excite spin polarized currents at the surface of these materials in order to investigate their decay with the time-of-flight spectrometer.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Ulrich Höfer