Heidelberg 2015 – wissenschaftliches Programm
Q 12.3: Vortrag
Montag, 23. März 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  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.
 P. Soltan-Panahi et al., Nature Physics 8, 71 (2012).