THz spectroscopy has sprung to the forefront of the study of quantum materials in recent years. With these recent advances, we can now bridge the gap between the capabilities of photonics in the infrared and visible range, and those of electronics in the microwave.

I will describe our recent explorations into the physics of topological insulator Bi2Se3 thin films, and of a multiferroic quantum magnet Sr2FeSi2O7 single crystals using terahertz spectroscopy.