Description:

A semiconductor quantum dot (QD) represents an ideal model system for the investigation of quantum mechanical electron-electron interactions. This is because Coulomb blockade (a result of the negative electrons repelling one another) allows electrons to be added or removed one by one simply with a gate electrode. As a result, the electrical, optical, and magnetic properties are tunable. An exciton complex consists of a hole bound to the electrons in a QD. The spatial extent of the exciton wave reflects both the confinement of the QD and the Coulomb (electrical) interactions and can be probed by applying a magnetic field, B. For neutral excitons, the exciton energy increases quadratically with B, the so-called diamagnetic shift.  However, the behavior of charged excitons is less well-known and potentially much more interesting because of the more elaborate Coulomb interactions. The charged exciton investigated is very easily ionized in both bulk semiconductors and quantum wells and so by turning to QD’s we have entered a new regime where the Coulomb interactions can dominate the response to a magnetic field.
 

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