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Mean-field description of a rotating dipolar Bose gas in an annular trap and of a rapidly rotating two-component Bose gas

### Elife Karabulut

**Friday, 22 March 2013, 14:00**

Matfys library

**Abstract**:

The high degree of tunability and flexible control are the two important features associated with cold atomic gases,
which have so far paved the way for various applications including ow-dimensional systems, confining potentials with
different functional forms, multi-component Bose-Einstein condensates (BECs), quantum gases with different inter-particle interactions, etc.
Systems with one or more of these properties exhibit remarkably rich physics, which is interesting to study either experimentally or theoretically.
A good example to see the effect of such properties coexisting in a system is a low-dimensional dipolar Bose gas.
Low-dimensional confinements offer the opportunity to study the effects of dipolar interaction without instability problems
caused by the head-to-tail alignment of dipoles in three dimensions. To investigate the anisotropic character of the interaction,
we consider a rotating dipolar BEC confined in an annular trap for an arbitrary orientation of the dipoles with respect to their plane of motion.
Within the mean-field approximation, we find that the system exhibits different vortex configurations depending on the polarization angle of the
dipoles and on the relative strength between the dipolar and the contact interactions. Another example of such a system is a two-component BEC
confined in an anharmonic potential. Confining potentials rising more steeply than quadratically allow the study of rapidly rotating BECs,
which introduce many novel phases. This picture becomes even more interesting in the case of a multi-component BEC .
We investigate the rotational properties of a two-component BEC, which is confined in an anharmonic trapping potential using both numerical
and analytic methods. More specifically, with the use of a variational approach we derive analytically the phase diagram of the system as a
function of the rotational frequency of the trap and of the coupling constant for sufficiently weak values of the anharmonicity and of the coupling.
The more general structure of the phase diagram is investigated numerically. We compare our results with the ones of (i) a single-component BEC
confined in an anharmonic potential, and (ii) a two-component BEC, which is confined in a harmonic trapping potential.