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<div align="center"><font face="Times New Roman"
color="#000000"><b>Seminar on</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Modern Optics and Spectroscopy</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><i><b>Slow electron cooling and spin blockade in
colloidal quantum dots</b></i></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Philippe Guyot-Sionnes</b>,</font></div>
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color="#000000">University of Chicago</font></div>
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<div align="center"><font face="Times New Roman"
color="#000000">Tuesday, November 18, 2008</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">12:00
- 1:00 p.m.</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">I
will discuss two separate effects that arise from the low density and
small degeneracy of states of quantum dots. The first one
is the "phonon bottleneck". This refers to the slow
electron cooling expected in dots due to the small electron-phonon
coupling and the large energy mismatch between electronic states and
phonons. It had long been expected but remained elusive.
We observed it between the 1Pe and 1Se conduction states with
colloidal dots designed to reduce three alternate ways by which energy
is dissipated, via coupling to holes, via intermediate trap states and
via molecular vibrations. The second effect is the
magneto-resistance at low fields of 50 mT that we observed in dot
films, and attributed to a spin blockade in the singly degenerate 1Se
spin state.</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">Grier
Room, MIT Bldg 34-401</font></div>
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color="#000000">Refreshments served after the lecture</font></div>
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