Time-resolved ARPES (tr-ARPES)

Time-resolved ARPES (tr-ARPES) extends the power of angle-resolved photoemission spectroscopy into the time domain, enabling direct observation of ultrafast electron dynamics on femtosecond to picosecond timescales. In a pump-probe configuration, a short infrared or visible pump pulse drives the material out of equilibrium, and a delayed ultraviolet or extreme-ultraviolet probe pulse ejects electrons whose energy and momentum are then measured, yielding snapshots of the transient spectral function as the system evolves. This approach makes it possible to both follow how excited states relax through separate distinct interaction channels via their characteristic timescales, and to access normally unoccupied electronic states that are invisible to conventional ARPES.

Over the past two decades, tr-ARPES has become one of the most powerful tools in quantum materials research, delivering momentum-resolved insight into phenomena ranging from light-driven phase transitions and Floquet-engineered band structures to exciton formation in atomically thin semiconductors and the ultrafast dynamics of high-temperature superconductors. In our group, tr-ARPES is used both to probe nonequilibrium many-body dynamics and to explore how light can be used to transiently control and engineer electronic structure.