Stuttgart 2012 – wissenschaftliches Programm
Q 35.9: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.I+II
Orbital Physics with Ultracold Atoms in Higher Bands of an Optical Lattice — •Thorge Kock, Matthias Ölschläger, Georg Wirth, and Andreas Hemmerich — Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
Atoms trapped in optical lattices have been used successfully to study many-body phenomena. But the positive definite ground-state wavefunction of bosons limits their usefulness for simulating many-body systems of interest. Such limitations, however, do not apply to excited states of bosons.
Using a two-dimensional optical square lattice with adjustable time phase difference, we can selectively excite a large fraction of atoms into higher bands by means of a population swapping technique, where a collision-aided condensation to the band minima reestablishes coherence. Depending on the involved band and the lattice configuration, we can realize real-valued striped superfluid order parameters, or complex-valued order parameters which break time reversal symmetry.
Lifetimes of higher bands of up to 150 ms allow us to study the nature of the order parameter in the second band and phenomena like a topologically induced avoided band crossing between the 3rd and 4th band of our chequerboard lattice.