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(UMI)AAI9114419 http://hdl.handle.net/2142/19465 eng Wolfe, J.P. Snoke, David Wayne 2011-05-07T12:08:22Z 2011-05-07T12:08:22Z 10000-01-01 1990 Free excitons provide the only experimental system other than helium in which the behavior of particles with mass is known to follow Bose-Einstein statistics. I present experimental observations of the kinetic energy distribution of excitons in the direct-gap semiconductor Cu$\sb2$O, both the triplet orthoexciton state and the singlet paraexciton state. The density and temperature of the exciton gas closely follow the phase boundary for Bose-Einstein condensation. At the highest densities, the lower-lying paraexcitons take on an anomalous energy distribution with a sharp, high-energy edge. This odd distribution of particle energies may be associated with Bose-Einstein condensation into a state with nonzero momentum. Indeed, the excitons leave the region of their creation at supersonic velocities. In addition to the exerimental observations, I also present theoretical models for several aspects of this non-equilibrium system. I model the equilibration of a nearly-ideal boson gas and find that a significant time is required for the approach to condensation. I also propose a new mechanism for spin-flip conversion between the orthoexciton and paraexciton states. Finally, I model the temperature and density of the excitons in steady state based on known classical kinetic effects in semiconductors, and I estimate the effects of Bose-Einstein statistics on these processes. Made available in DSpace on 2011-05-07T12:08:22Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9114419.pdf: 7666347 bytes, checksum: 9673e2771a364d8170a44667f811ceff (MD5) Previous issue date: 1990 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:37:09Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:15:13-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9114419 Copyright 1990 Snoke, David Wayne Physics, Condensed Matter Bose-Einstein condensation of excitons in cuprous oxide text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.