In this study we investigate the properties of trapped atoms
subjected to rapid rotations. The study is divided into two distinct
parts, one for fermions, another for bosons. In the case of the
degenerate Fermi gas we explore the density structure of
non-interacting cold atoms when they are rotated rapidly. On the
other hand, for rapidly rotating two component Bose condensate, we
search for new lattice structures in the presence of contact and
dipolar interactions.
First, the density structure of Fermi gases in a rotating trap is
investigated. We focus on the anisotropic trap case, in which two
distinct regimes, two and one dimensional regimes, depending on
rotation frequency and anisotropy are observed. Two regimes can be
illustrated by a simple description of maximum number of states
between two Landau levels, which is strongly related to the
dimensionality of the system. The regimes are separated from each
other by a minimum point in this description. For small anisotropy
values the density profiles show a step structure where each step is
demonstrated by an elliptical plateau. Each plateau represents a
Landau level with a constant density. The local density
approximation describes the two dimensional regime with a perfect
similarity in the structure of fermion density. The case for one
dimensional regime is a little different from the two dimensional
case. For large anisotropy values the Friedel oscillation is the
dominant aspect of the density profiles. The density profiles show
gaussian structure along the direction of strong trapping, and a
semicircular form with prominent oscillations along the weak
confining direction. Again, the system is nicely described by local
density approximation in this regime. A smooth crossover between two
regimes is observed, with a switching from a step structure profile
to a soft edge transition with Friedel oscillations. At finite
temperatures, the step structures are smeared out in two dimension.
In one dimensional regime the Friedel oscillations are cleaned as
soon as the temperature is turned on.
The second part of the study is devoted to the investigation of
different lattice structures in two component Bose condensates
subjected to very fast rotation, this time in the presence of
interactions. We explore the existence of new vortex lattice
structures for dipolar two component condensates scanning a wide
range of interaction strengths. We introduce a phase diagram as a
function of intra and inter-component interactions showing different
type of vortex lattice structures. New types of lattice structures,
overlapped square and overlapped rectangular, emerge as a
result of dipolar interactions and s-wave interaction for a two
component condensate. The region where the attractive
inter-component interactions dominate the repulsive interactions, the
overlapped lattices are formed. The intra-component interactions,
which defines the behavior of each component inside, result in
different type of lattices by changing the strength of interactions.
Two different limits of phase diagram reproduce the results of
ordinary two component and dipolar one component Bose condensates.
The results of calculation are in agreement with the results of
previous studies for two regimes.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12613282/index.pdf |
| Date | 01 June 2011 |
| Creators | Ghazanfari, Nader |
| Contributors | Ozpineci, Altug |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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