Insulating, conducting, and superconducting phases can be identified through their characteristic low-energy response. We discuss experiments that employ ultrashort coherent THz pulses and direct field-resolved detection to probe time-varying correlations of charge carriers in semiconductors and superconductors. These experiments detect 1s-2p intra-exciton resonances of photoexcited e-h gases in GaAs quantum wells. Stimulated emission from intra-excitonic transitions is observed in Cu2O, between 3p and 2s exciton states. Finally, we discuss the formation kinetics of Cooper pairs from nonequilibrium quasiparticles as observed in the transient THz response of the high-TC superconductor Bi-2212.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics