The large dielectric constant and small effective mass in a semicon- ductor allows a description of its electronic states in terms of envelope wavefunctions whose energy. time, and length scales are mesoscopic. i.e., halfway betWeen those of atomic and those of condensed matter systems. This property makes it possible to demonstrate and inves- tigate many quantum mechanical, many-body, and quantum kinetic phenomena with tabletop experiments that would be nearly impos- sible in Other systems. This, along with the ability to custom-design semiconductor nanostructures, makes semiconductors an ideal labo- ratory for experimental investigations. We present an overview of some of the most exciting results obtained in semiconductors in recent years using the technique of ultra fast nonlinear optical spec- trocopy. These results show that Coulomb correlation plays a major role in-semiconductors and makes them behave more like a strongly interacting system than like an atomic system. The results provide insights into the physics of strongly interacting systems that are relevant to other condensed matter systems. but not easily accessible in other materials.
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