Hanns-Christoph Nägerl
Realization of an Excited, Strongly-Correlated, Quantum Gas Phase
We realize a strongly-correlated 1D quantum gas of bosons with strong attractive interactions known as the super-Tonks-Girardeau (sTG) gas [1]. For this, we load a Bose-Einstein condensate of Cs atoms into an array of ``tube-like" 1D traps generated by a 2D optical lattice and exploit the tunability of the strength of the interaction near a Feshbach resonance. When the 3D scattering length is increased towards and beyond the length scale set be the tight transversal confinement, we observe a confinement-induced resonance (CIR) that allows us to tune the effective 1D-interaction parameter g_1D to large positive and large negative values. By tuning to large positive values for g_1D we tune from the 1D mean field regime deeply into the Tonks-Girardeau (TG) regime. We then cross on the CIR into the sTG regime of strong attractive interactions. We find that the system in this excited many-body state is surprisingly stable. We diagnose the crossover from repulsive to attractive interactions in terms of the stiffness and the energy of the system [2].
[1] G. Astrakharchik et al., Phys. Rev. Lett. 95, 190407 (2005).
[2] E. Haller et al., manuscript submitted (2009).
