Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 12: Quantum Gases: Bosons II

Q 12.3: Talk

Monday, March 23, 2015, 15:00–15:15, P/H2

Twisted superfluidity in optical lattices — •Ole Jürgensen, Klaus Sengstock, and Dirk-Sören Lühmann — Institut für Laserphysik, Universität Hamburg

An unconventional quantum phase with a complex order parameter has been observed recently in a hexagonal optical lattice [1] but still lacks a conclusive theoretical understanding. We show how correlated pair tunneling in the extended Bose-Hubbard model can drive the transition to this twisted superfluid phase. We present the full phase diagram showing a multitude of quantum phases including checkerboard insulators, supersolids and pair superfluids. Furthermore, off-site interactions support dimerized insulator phases where particles are delocalized on several lattice sites. For two components we find twisted superfluid phases already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid.

[1] P. Soltan-Panahi et al., Nature Physics 8, 71 (2012).