Ultrafast THz spectroscopy of correlated electrons: from excitons to Cooper pairs

• Published in: Physica Status Solidi (b) Vol. 243; no. 10; pp. 2414 - 2422
• Main Authors: Kaindl, R. A., Huber, R., Schmid, B. A., Carnahan, M. A., Hägele, D., Chemla, D. S.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin WILEY-VCH Verlag 01-08-2006; WILEY‐VCH Verlag; Wiley
• Subjects: 71.35.−y; 74.25.Gz; 74.40.+k; 78.47.+p; 78.67.De; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Physics; Properties of type I and type II superconductors; Quantum wells; Superconductivity; Transport properties (electric and thermal conductivity, thermoelectric effects, etc.); Gallium arsenides; Semiconductor materials; Quantum wells; Excited states; Quasiparticles; Electron correlations; THz range; Stimulated emission; Excitons; Ultrashort pulse; Cooper pairs; High-Tc superconductors; Ultrafast process
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200668077

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‐T C superconductor Bi‐2212. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)