Mass-imbalanced atomic mixtures in one- dimensional optical lattices

The physics of binary atomic mixtures in optical lattices is of fundamental importance for the

realization of quantum magnetism, pairing phenomena and unconventional superfluidity. A

special role is played by mass imbalance between the two species, which controls the symmetry

of the magnetic Hamiltonians realized in the strong coupling limit at half filling, and which,

even away from half filling, allows the realization of unconventional crystalline phases made of

composite objects (as, e.g., bound dimers) with effective off-site interactions.

Here we present a comprehensive numerical study of mass-imbalanced mixtures in one-

dimensional optical lattices in the case of hardcore interactions between particles of the same

species - namely we describe either spinful fermions, or spinful hardcore bosons, or hardcore

boson/fermion mixtures. Our main results are the persistence of spin-charge separation and of

an effective SU(2) symmetry even for strong mass imbalance in the repulsive case; the

appearance of crystalline phases for extreme mass imbalance both in the attractive and in the

repulsive case; and the fundamental role played by both mass imbalance and a trapping

potential in order to observe fully paired phases in attractive mixtures, even in presence of

population imbalance.

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