Dresden 2011 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 24: Quantum Gases: Opt. Lattice 1

Q 24.2: Vortrag

Mittwoch, 16. März 2011, 10:45–11:00, HSZ 02

A mulitband ground-state superfluid — •Parvis Soltan-Panahi, Julian Struck, Dirk-Sören Lühmann, Andreas Bick, Wiebke Plenkers, Rodolphe Le Targat, Patrick Windpassinger, and Klaus Sengstock — Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

Superfluid bosonic atoms confined in a 3D optical lattice are usually very well described by a single quasi-momentum state in the lowest Bloch band (s-band). In this regime, interaction effects are small and can mostly be treated at a mean-field level.

Here, we report on the experimental realization of an interaction induced mixing of the s- and p-band states in a shallow, spin-dependent hexagonal lattice in the superfluid regime. This novel phase occurs for a certain class of spin-mixtures and can be unambiguously determined by a clear reduction of the six-fold rotational symmetry to a three-fold symmetry of the many-body state in momentum space. Remarkably, the fully correlated two-particle interaction plays here the major role, which is usually only observed in strongly interacting systems.

We theoretically describe this novel mulit-band superfluid ground-state phase as a second-order quantum phase transition. This is characterized by a twisted quantum mechanical phase between s- and p-band superfluid fractions, which leads to the very characteristic momentum spectrum of the different spin-components.