[MOS] November 18, 2008

[Zina Queen]

Seminar on

Modern Optics and Spectroscopy

Slow electron cooling and spin blockade in colloidal quantum dots

Philippe Guyot-Sionnes,
University of Chicago

Tuesday, November 18, 2008

12:00 - 1:00 p.m.


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.



Grier Room, MIT Bldg 34-401
Refreshments served after the lecture
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