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PROPERTIES OF HARD-CORE BOSONS IN POTENTIAL TRAPS
by
Aditya Raghavan
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(PHYSICS)
August 2009
Copyright 2009 Aditya Raghavan
Object Description
| Title | Properties of hard-core bosons in potential traps |
| Author | Raghavan, Aditya |
| Author email | aditya.raghavan@gmail.com; adityara@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Physics |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-06-05 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-08-08 |
| Advisor (committee chair) | Haas, Stephan W. |
| Advisor (committee member) |
Kresin, Vitaly Dappen, Werner Bickers, Eugene Wang, Chunming |
| Abstract | Following the recent advances in controlling ultracold quantum gases that have led to the realization of boson and fermion condensation, we present computational studies of one-dimensional bosons on optical lattices. These systems have proven to be a great tool to study exciting new frontiers of condensed matter, from exotic phase transitions to nonequilibrium phenomena.; In this thesis we study one-dimesional hard-core bosons, which is a limiting case of the Bose-Hubbard model when the on-site repulsion becomes infinite. Previously, this model has been well studied and is known to admit superfluid and Mott insulating phases. The time evolution of hard-core bosons in a one-dimensional trap is studied. Using an exact numerical approach, we study the ratio of the breathing mode and sloshing mode vibrations of the one-dimensional gas. We then study the evolution in a parametrically driven trap. Using an exact numerical approach, the dynamics of the system is determined as the trap curvature is modulated. The response is found to be markedly different in the superfluid and Mott-insulating regimes. By measuring the frequency dependence of the zero-momentum peak of the momentum distribution function, parametric excitations are observed, which depend on the phases present in the system. It is shown that these excitations closely match the quasi-particle spectrum, thus providing a useful tool to probe the low energy excitations of the system in its various phases.; We then revisit the one-dimensional Bose-Hubbard model with a finite on-site repulsion. We study the effects of disorder on interacting trapped bosons. At small to moderate disorder strengths it is observed that if there is a Mott plateau at the center of the trap in the clean limit, phase coherence increases as a result of turning on disorder. The localization effects due to correlation and disorder compete against each other, resulting in a partial delocalization of the particles in the Mott region. We show that in this regime delocalization can lead to an increase in phase coherence. |
| Keyword | physics; condensed matter physics; optical traps; quantum gases; ultracold atoms; Bose Hubbard model; bosons; hard core bosons; time dependent Hamiltonian |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2549 |
| Rights | Raghavan, Aditya |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-RAGHAVAN-3065 |
| Archival file | uscthesesreloadpub_Volume56/etd-RAGHAVAN-3065.pdf |
Description
| Title | Page 1 |
| Full text | PROPERTIES OF HARD-CORE BOSONS IN POTENTIAL TRAPS by Aditya Raghavan A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (PHYSICS) August 2009 Copyright 2009 Aditya Raghavan |
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