Bose-Einstein condensation of excitons in uniaxially stressed cuprous oxide

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Lin, Jia Ling

• Physics, Condensed Matter

Statement dc:rights

• Copyright 1994 Lin, Jia Ling

Language dc:language

eng

Identifier

AAI9522140
(UMI)AAI9522140

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20190