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Title: On the formation of stationary spatial patterns of luminescence in two-dimensional exciton systems
Authors: Paraskevov, Alexander V.
Keywords: Quantum well excitons
Collective effects
Pattern formation
Issue Date: 2010
Publisher: © A.V. Paraskevov
Abstract: The thesis is organized as follows: In Chapter 1 the introduction and the description of motivating experiments are given. It also contains the formulation of the problems for the research. Chapter 2 describes two kinetic mechanisms suggested to explain the ring-shaped luminescence pattern formation and, to investigate the influence of one of them, the results of molecular dynamics simulation of a spatiotemporal evolution of the locally photoexcited electrons and holes localized in two separate layers. In particular, it is shown that the ring-shaped spatial pattern of luminescence can be formed due to the strong in-layer Coulomb interactions in the excitation spot at high photoexcitation power. The strong interactions become possible because of the bilayer geometry. In Chapter 3 a simple microscopic mechanism which explains the linear dependence of the radiative lifetime of free-moving two-dimensional excitons on their effective temperature is suggested. It is shown that there exists a characteristic effective temperature (of about few Kelvin) defined by exciton-acoustic phonon interaction at which the radiative lifetime is minimal. Below this temperature the lifetime starts to increase with decreasing temperature. The correspondence with previous theoretical and experimental results is discussed. In Chapter 4 the external ring fragmentation is considered under the assumption that excitons at the ring become statistically degenerate at low temperatures. In particular, the exciton condensate density at the ring has been found as a function of the polar angle at zero temperature with the involvement of exciton formation and recombination processes. Starting from the quasi one-dimensional Gross-Pitaevskii equation with a spatially uniform pumping-and-decay term, an exact analytical solution is derived yielding the spatial fragmentation of the exciton ring in a certain range of parameters. Chapter 5 is Appendix. It contains some results which are essential for the whole thesis.
Description: A Doctoral Thesis. Restricted access with a Moratorium period of 20 years ending 5th October 2030. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.
URI: https://dspace.lboro.ac.uk/2134/7107
Appears in Collections:Closed Access PhD Theses (Physics)

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