Due to the rapid progress in atomic physics and quantum optics over the last twenty years, it has become possible to cool atoms down to extremely low temperatures. In these regimes, the atoms can no longer be considered as classical particles, but their quantum nature has to be taken fully into account. So far, the most spectacular milestone in these developments has been the experimental realization of Bose-Einstein condensation in atomic gases in 1995, which has spawned a vast amount of exciting further activities. From a theoretical point of view, the study of ultracold atomic gases is particularly attractive as the interactions between the particles are very weak. This makes them amenable to a much simpler and detailed description than it is possible for other comparable systems, e.g., of solid-state physics.

If you are not familiar with this fascinating and flourishing field, that has been awarded the Nobel Prizes in Physics
in 1997
and 2001,
the following reviews might provide a good starting-point:

W. Ketterle, D. M. Stamper-Kurn, and D. S. Durfee,
Making, probing and understanding Bose-Einstein condensates

F. Dalfovo, S. Giorgini, L. P. Pitaevskii, and S. Stringari,
Theory of Bose-Einstein condensation in trapped gases

Many further links can be found at the Georgia Southern University.

In our group, we have studied various aspects of the quantum-statistical and dynamical behavior of ultracold quantum gases and, in particular, Bose-Einstein condensates. Work by our group members in this area is listed below.

O. Zobay and Georgios M. Nikolopoulos, Phys. Rev. A 73, 013620 (2006)

O. Zobay and Georgios M. Nikolopoulos, Phys. Rev. A 72, 041604(R) (2005)

In combination with results from variational perturbation theory [2], this research has provided a deeper understanding of how an increasingly inhomogeneous potential suppresses critical fluctuations and changes nonperturbative into perturbative physics: the critical properties of homogeneous Bose gases are dominated by long wavelength critical fluctuations which have to be described nonperturbatively, whereas condensation in sufficiently inhomogeneous, e.g., harmonic, potentials can be treated perturbatively. Studying the critical properties of Bose gases in general power-law potentials allows to smoothly interpolate between these limits.

O. Zobay, Phys. Rev. A 73, 023616 (2006)

O. Zobay, G. Metikas, and H. Kleinert, Phys. Rev. A 71, 043614 (2005)

O. Zobay, G. Metikas, and G. Alber, Phys. Rev. A 69, 063615 (2004)

O. Zobay, J. Phys. B 37, 2593 (2004)

G. Metikas, O. Zobay, and G. Alber, Phys. Rev. A 69, 043614 (2004)

G. Metikas, O. Zobay, and G. Alber, J. Phys. B 36, 4595 (2003)

G. Metikas and G. Alber, J. Phys. B 35, 4223 (2002)

G. Alber and G. Metikas, Appl. Phys. B 73, 773 (2001)

G. Alber, Phys. Rev. A 63, 023613 (2001)

Our proposed scheme has recently been realized by a number of experimental groups.

O. Zobay and B. M. Garraway, Phys. Rev. A 69, 023605 (2004)

O. Zobay and B. M. Garraway, Phys. Rev. Lett. 86, 1195 (2001)

O. Zobay and B. M. Garraway, Phys. Rev. A 61, 033603 (2000)

However, by taking additional measures it is nevertheless possible to create bright solitons. Motivated by the analogy to conventional nonlinear optics, we have devised a method to launch bright gap solitonlike structures in condensates confined in optical traps. Their formation relies on the dynamics of the atomic internal ground states in two far-off-resonance counterpropagating left- and right-circularly polarized laser beams. The soliton motion can be controlled by suitable additional optical and magnetic fields. As an illustration we have discussed a nonlinear atom-optical Mach-Zehnder interferometer based on gap solitons.

S. Pötting, O. Zobay, P. Meystre, and E. M. Wright, J. Mod. Opt. 47, 2653 (2000)

O. Zobay, S. Pötting, P. Meystre, and E. M. Wright, Phys. Rev. A 59, 643 (1999)

Prof. Dr. Gernot Alber

Institut für Angewandte Physik

Hochschulstraße 4a

64289 Darmstadt, Germany

+49-6151/16-20400 (fax: 20402)

gernot.alber@physik.tu-...