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Ultrafast THz Spectroscopy: From Excitons to Cooper Pairs


Ultrafast spectroscopy is a powerful tool to study key microscopic processes that occur on short timescales in molecules, solids, and biological systems. I will discuss experiments that employ coherent THz light pulses to study the dynamics of low-energy excitations and carrier correlations in semiconductors and superconductors. Bound electron-hole pairs (excitons) exhibit characteristic inter-level transitions analogous to atoms. This enables “intra-excitonic” spectroscopy as a novel tool to directly map out excitonic phase diagrams and to uncover exciton formation and ionization dynamics. In high-T C superconductors such as Bi-2212, the THz-frequency electromagnetic response couples directly to Cooper pairs and quasiparticles. This reveals a bimolecular kinetics of charge pair formation that occurs after transient depletion of the superconducting condensate. Such experiments trace correlated states via their transient low-energy response and motivate further ultrafast studies of microscopic processes and collective excitations in nanoscale and correlated materials.

(Everyone is welcome to attend)

Dr. Robert A. Kaindl is a candidate for the Experimental Condensed Matter Physics Position.