Studying spin–charge conversion using terahertz pulses

Spin–charge conversion is a spin–orbit coupling phenomena where electrical currents can generate transverse spin currents and vice versa. It is one of the central topics in spintronics and widely applied to manipulate the spin and charge degrees of freedom in materials. Previous research on spin–charge conversion was mainly carried out by transport measurements, which lies in the (quasi)equilibrium and DC/low-frequency limit. The recent development of THz emission spectroscopy applied to this field provides additional insights into the dynamics of the spin–charge conversion process, i.e., its ultrafast timescales. Here, the underlying physics and the latest progress of THz studies on spintronics are introduced. The technical details and some features of this technique are summarized, including spin current generation, signal detection, and data analysis. Finally, some possible developments are discussed as well as future research and applications.