Quantum saturation and condensation of excitons in copper (I) oxide

"Recent experiments on high-density excitons in Cu$\sb2$O provide evidence for degenerate quantum statistics and Bose-Einstein condensation of this nearly ideal gas. We model the time dependence of this bosonic system including exciton decay mechanisms, energy exchange with phonons, and interconversion between ortho (triplet-state) and para (singlet-state) excitons, using parameters for the excitonic decay, the coupling to acoustic and low-lying optical phonons, Auger recombination, and ortho-para interconversion derived from experiment. The single adjustable parameter in our model is the optical-phonon cooling rate for Auger and laser-produced hot excitons. We show that the orthoexcitons move along the phase boundary without crossing it (i.e., exhibit a ""quantum saturation""), as a consequence of the balance of entropy changes due to cooling of excitons by phonons and heating by the non-radiative Auger two-exciton recombination process. Our study implies that the Auger annihilation rate for para-para collisions is much smaller than that for ortho-para and ortho-ortho collisions due to the band structure of the material, explaining why, under the given experimental conditions, the paraexcitons condense while the orthoexcitons fail to do so. Furthermore, we review the band structure underlying the properties of excitons in Cu$\sb2$O and connect these properties to the Auger recombination process of excitons."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics, Condensed Matter

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Kavoulakis, Georgios

Contributors dc:contributor

• Baym, Gordon A.

• Physics, Condensed Matter

Statement dc:rights

• Copyright 1996 Kavoulakis, Georgios

Language dc:language

eng

Identifier

9780591088007
AAI9702557
(UMI)AAI9702557

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/23470