2026-09-21T14:14:28Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/20190 2023-07-10 col_2142_5131 col_2142_8859 com_2142_5130 com_2142_8858 com_2142_234

Lin, Jia Ling 2011-05-07T12:31:42Z 2011-05-07T12:31:42Z 10000-01-01 1994 Excitons in Cu$\sb2$O have been demonstrated to be a nearly ideal gas of bosons, providing a unique system for studying Bose-Einstein statistics and Bose-Einstein Condensation of an ideal gas in the laboratory. In this study, I have applied uniaxial stress to optimize the conditions for a Bose-Einstein Condensation phase transition of the excitons in this crystal. Using time-resolved photoluminescence, an enhanced quantum degeneracy of the orthoexcitons is observed in this stressed crystal due to the lowered multiplicity of the orthoexciton ground state, although no evidence of the condensation phase of the orthoexcitons is observed. In contrast, I have found compelling evidence for Bose-Einstein Condensation of the singlet paraexcitons in uniaxially stressed Cu$\sp2$O. When the paraexciton gas attains a particle density exceeding the critical density for Bose-Einstein condensation, the paraexciton spectrum develops an extra component at low energy which is about 0.1-0.3 meV above the zero-kinetic-energy state. I also observe an anomalous spatial transport of the paraexcitons when this low-energy component is present. This ballistic wave-like (or drift-like) motion occurs at an expansion rate 3 $\times$ 10$\sp5$ cm/sec to 4 $\times$ 10$\sp5$ cm/sec, roughly correlated with a blue-shift of 0.1-0.3 meV for the low-energy component of the paraexcitons. I therefore interpret the low-energy component of the paraexcitons as a Bose-Einstein condensation peak. Made available in DSpace on 2011-05-07T12:31:42Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9522140.pdf: 6592884 bytes, checksum: 01dfe8dc6e4971132fa8ce1653fcf5a5 (MD5) Previous issue date: 1994 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:42:14Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:18:20-05:00 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 AAI9522140 (UMI)AAI9522140 http://hdl.handle.net/2142/20190 eng Copyright 1994 Lin, Jia Ling Physics, Condensed Matter Bose-Einstein condensation of excitons in uniaxially stressed cuprous oxide text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.