December ICAM Meeting
Professor Dan Chemla
University of California at Berkeley
1 Cyclotron Road, MS-66
Berkeley, CA 94720
(510) 643-2735
It is clear that understanding many particle systems is
one of the outstanding issues of modern physics. However, the U.S. condensed matter
physics community has almost exclusively concentrated its attention on strongly correlated
materials, such the high-Tc
cuprates or the antiferromagnetic oxides, and has completely ignored the important
investigations of correlation effects performed during the last decade in semiconductors
through time-resolved nonlinear optical spectroscopy techniques. These materials play a
very special role in that context; they have been around for quite some time, a lot is
known about their fundamental properties, and sound theoretical techniques, based on
well-established approximations, are at hand for describing their ground state and linear
properties. Because of their technological importance, almost perfect samples are now
available. Finally, the energy and time scales of their elementary excitations are well
matched to that of state-of-the-art optical and transport spectroscopic techniques.
Therefore they form a perfect laboratory for extending our field of investigation of
correlation effects in regimes previously inaccessible. In particular, time-resolved
nonlinear optical spectroscopy of semiconductors has been thoroughly applied to
investigate the creation of elementary excitations whose dynamics evolve significantly on
short time and short length scales. This has revealed a new regime of correlation where
the fluctuations of the ́order parametersî become important and the mean-field pictures
break down, thus raising important questions about the validity of well-established
approximations in the quasi-static regime. This combination of extreme density dependence
and ultrafast kinetics makes the behavior of electronic excitations in semiconductors and
their heterostructures a fascinating topic at the frontier of condensed matter physics.