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SUMMARY:Ultrafast measurements of the nonequilibrium charge-transfer state
  of Sr2CuCl2O2 - Jesse Petersen\, University of Oxford
DTSTART:20091021T101500Z
DTEND:20091021T111500Z
UID:TALK19693@talks.cam.ac.uk
CONTACT:Michael Sutherland
DESCRIPTION:The excitation spectrum of magnetic insulators is of central c
 oncern in condensed matter physics. Nonetheless\, many properties of insul
 ating copper\noxides remain poorly understood\, and the optical gap excita
 tion near 2 eV is an important example. This excitation transfers electron
 s from oxygen to copper\nions within the plane\, creating electrons and ho
 les which then interact with surrounding electronic states\, with magnetic
  excitations\, with phonons\, and with each other. The relative significan
 ce of these interactions is not yet clear.\n\nIn this talk I will describe
  our efforts to characterise the photoexcited state of Sr2CuCl2O2\, an und
 oped copper oxide. We create electrons and holes with a femtosecond laser 
 pulse\, and then use ultrafast\, time-resolved spectroscopic probes to exa
 mine the non-equilibrium state as it decays. Measurements with THz\npulses
  give the transient optical conductivity at low energies\, from which we e
 stimate the photocarrier contribution to long-range transport\, as well as
  the\ncharacteristic energy scale for dynamical conductivity. Broadband me
 asurements of optical transmission in the visible spectrum reveal the phot
 o-production of low-energy bosons\, whose energy and decay dynamics are in
  agreement with the THz measurements.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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