Phase diagram of imbalanced strongly interacting fermions on a one-dimensional optical lattice

Theja N. De Silva

Ariel Sommer, Lawrence W. Cheuk, Mark Ku +3 more

Tommaso Roscilde, C. Degli Esposti Boschi, M. Dalmonte

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 trapped cold atoms.

Alberto Anfossi, Luca Barbiero, Arianna Montorsi

We show that the Hubbard Hamiltonian with particle-assisted tunneling rates---recently proposed to model a fermionic mixture near a broad Feshbach resonance---displays a ground-state phase diagram with superfluid, insulating, and phase-separated regimes. In the latter case, when the populations are balanced the two phases coexist in microscopic antiferromagnetic domains. Macroscopic phase segregation into a high-density superfluid of molecules and a low-density Fermi liquid of single atoms appears in the density profile above a critical polarization ${p}_{c}$.

V. V. França, Dominik Hörndlein, Andreas Buchleitner

We deduce an expression for the critical polarization ${P}_{C}$ below which the Fulde-Ferrell-Larkin-Ovchinnikov state emerges in one-dimensional lattices with spin-imbalanced populations. We provide and explore the phase diagram of unconfined chains as a function of polarization, interaction, and particle density. For harmonically confined systems, we supply a quantitative mapping, which also allows applying our phase diagram for confined chains. We find analytically and confirm numerically that the upper bound for the critical polarization is universal: ${P}_{C}^{\mathrm{max}}=1/3$ for any density, interaction, and confinement strength.

J. P. Kestner, Luming Duan