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We numerically determine the very rich phase diagram of mass-imbalanced binary mixtures of hardcore bosons (or equivalently—fermions, or hardcore Bose/Fermi mixtures) loaded in one-dimensional optical lattices. Focusing on commensurate fillings away from half-filling, we find a strong asymmetry between attractive and repulsive interactions. Attraction is found to always lead to pairing, associated with a spin gap, and to pair crystallization for very strong mass imbalance. In the repulsive case the two atomic components remain instead fully gapless over a large parameter range; only a very strong mass imbalance leads to the opening of a spin gap. The spin-gap phase is the precursor of a crystalline phase occurring for an even stronger mass imbalance. The fundamental asymmetry of the phase diagram is at odds with recent theoretical predictions, and can be tested directly via time-of-flight experiments on …
IOP Publishing
Publication date: 
1 Jan 2012

Tommaso Roscilde, C Degli Esposti Boschi, Marcello Dalmonte

Biblio References: 
Volume: 97 Issue: 2 Pages: 23002
EPL (Europhysics Letters)