We study ultrafast phenomena in quantum materials. A strong focus lies on the angular momentum of electrons (spin+orbit) and of the crystal lattice. The associated processes often coincide with the femtosecond time scale and, thus, terahertz frequency scale.

Consequently, to study such extremely fast dynamics, we develop novel tools like ultrafast ampere-meters, ohm-meters and strong terahertz voltage sources. They greatly rely on femtosecond optical pulses and electromagnetic transients in the still elusive frequency range from 1 to 30 terahertz. To better understand our experimental results, we work out simple theoretical models.