ELFT HÍRADÓ

["Szokefalvi Nagy Zoltan" <sznagy AT rmki.kfki.hu>]

                                MEGHIVÓ



                           RMKI Szeminárium

           A 2010. évi Zimányi Nehézionfizikai Téli Iskolával
                           közös rendezvény



                           Prof. Selim JOCHIM
               MPI for Nuclear Physics, Heidelberg, Germany


               'Extremely dilute, but strongly correlated:
                   Experiments with ultracold  fermions'



                  2010. november 29. (hétfő), du. 2 óra
               KFKI RMKI III. épület 2. emeleti Tanácsterem



Előadáskivonat:

Ultracold gases have been a fantastic playground for studying strongly
interacting many-body systems, largely because the interaction strength
between the atoms could be tuned at wish using so-called Feshbach
resonances. In particular, researchers succeeded to prepare fermionic
gases in which the scattering length is much bigger than the interparticle
spacing, which in turn is much larger than the range of the van-der-Waals
interaction. This generic system created in this way allowed the study of
complex many-body phenomena. The most prominent example was the BEC-BCS
crossover, which establishes a continuous link between the phenomena of
superfluidity of bosons and of the superconductivity of fermions.
Two-component mixtures of fermions with infinite scattering length have
been found to behave like an almost perfect fluid with viscosities eta/s
being close to the expected theoretical limits.

In our current experiments we study Fermi gases composed of three
distinguishable particles. At very large scattering length these systems
exhibit an approximate SU(3) symmetry, and they can be used as a
simplified model for quark matter. In our experiments, we have studied the
few-body physics of that system and found it to be governed by so-called
Efimov trimers, universal three-body bound states whose properties are
determined by the interparticle scattering length and a three-body
parameter. Recently, we directly observed such states for the first time
an measured their binding energy as a function of interaction strength*.
Currently, we are setting up an experiment that should allow us to study
many-body physics in that system, such as color superconductivity.