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SUMMARY:Control of photons\, electrons and spins in GaAs quantum wells usi
 ng acoustic fields - Dr. Paulo Santos\, Paul Drude Institute\, Berlin
DTSTART:20051205T141500Z
DTEND:20051205T151500Z
UID:TALK4584@talks.cam.ac.uk
CONTACT:K DAS GUPTA
DESCRIPTION:The dynamic modulation of the electronic and optical propertie
 s of\nGaAs low-dimensional structures by surface acoustic waves (SAWs)\npr
 ovides a convenient way of controlling photons\, carriers\, and\nspins. Ef
 ficient photon control takes place through the modulation of\nthe dimensio
 ns and optical properties of GaAs-based photonic\nresonators by the acoust
 ic field. The modulation creates a dynamic\noptical superlattice\, which a
 cts as an efficient optical switch.\nCarrier control employs the piezoelec
 tric field induced by the\nSAW. The latter forms three-dimensionally confi
 ned and mobile potentials\n(dynamic\nquantum dots\, DQDs) in an undoped qu
 antum well (QW) structure\, which\ntransport\nphotogenerated electron-hole
  pairs over hundreds of micrometers with the\nacoustic velocity.   More im
 portant\, photogenerated electron spins\ncan be coherently transported in 
 that way over distances approaching 100\nmicrometer\, which corresponds to
  an increase in the electron\nspin lifetime of approximately two orders of
  magnitude.  The long\nelectron spin lifetimes are attributed to the reduc
 tion of the\nspin scattering mechanisms due to the DQD confinement.  Final
 ly\,\napplication of an external magnetic field enables the spin state to 
 be\nmodulated during transport\, thus opening the way for application in\n
 spintronics.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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