Dissertation committee:
Δημήτριος Φραντζεσκάκης Καθηγητής (επιβλέπων), Φώτιος Διάκονος Αναπλ. Καθηγητής, Αθανάσιος Λαχανάς Καθηγητής
Summary:
The present thesis studies nonlinear matter waves in atomic Bose-Einstein
condensate mixtures,
composed of two different states of the same atomic species, and in particular,
macroscopic
nonlinear excited states of the condensate, in the form of matter wave
solitons. These excitations
have the form of: (a) a density dip in one component and a localized pulse in
the other
component, (b) beating structures composed of a subsequent density dip and a
density lump
in each component, (c) localized pulses in both components and (d) localized
density dips
in each component. Solitons of type (a) and (b) were recently observed
experimentally, in
the framework of the present thesis, as a result of the counterflow between the
condensate
components. Solitons of type (c) and (d) are predicted and anaylized for the
first time in a
system of binary condensates with spin-orbit interactions. The differnet types
of solitons
are studied in the framework of the mean-field theory and in particular using a
system
of two coupled Gross-Pitaevskii (GP) equations in (1+1) dimensions since the
relevant
epxeriments are perfomed in such a geometry. An analytical description of the
form, the
dynamics and the stability of the respective solitons is achieved, by
developing novel perurbative
analytical methods, based on the integrable limit of the corresponding GP
equations. Numerical
simulations are also employed, and are found to be in a very good agreement
with respect
to the analytical results and the experimental findings.
Keywords:
Solitons, Bose-Einstein condensates, Nonlinear waves, Mixtures, Ultracold atoms
