CPM Seminar

State-Resolved Exciton Dynamics in Quantum dots

Pat Kambhampati

Department of Chemistry
McGill University

Structures on the nanometer length scale offer a unique opportunity to investigate size effects on physical processes. Semiconductors are particularly appealing for size dependent investigation as they may be tuned on length scales crossing the excitonic Bohr radius, thereby inducing quantum confinement effects. Despite tremendous international effort, a clear understanding of the fundamental dynamics has remained elusive. Our initial experiments introduce a mixed time/frequency domain approach which yields the first quantitative measure of the size dependence of electron and hole relaxation dynamics in strongly confined semiconductor quantum dots. This approach was applied to provide the first direct observation of the eigenstate spectrum of the biexciton, completing the analogy of ‘artificial atoms’. Most recently, these state-resolved methods have been applied to produce the highest measured optical gain in quantum dots which were previously believed to show no gain, offering a rigorous approach to using quantum dots as gain media. Finally, these methods revealed the first state-resolved observation of coherent optical and acoustic phonons, resolving long standing issues of exciton-phonon couplings as well as yielding information on ‘decoherence free subspaces’.