Condensed Matter Physics Seminar
Note Special Time!
4 p.m., Monday, February 26, 2007
Room 1201, Physics Building
Ultrafast THz Spectroscopy: From Excitons to Cooper Pairs
(UC Berkeley and Lawrence Berkeley National Laboratory)
Abstract: 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-TC 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.
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