Abstract
We study the phase diagram of an SU(3)-symmetric mixture of three-component ultracold fermions with attractive interactions in an optical lattice, including the additional effect on the mixture of an effective three-body constraint induced by three-body losses. We address the properties of the system in D⩾2 by using dynamical mean-field theory and variational Monte Carlo techniques. The phase diagram of the model shows a strong interplay between magnetism and superfluidity. In the absence of the three-body constraint (no losses), the system undergoes a phase transition from a color superfluid (c-SF) phase to a trionic phase, which shows additional particle density modulations at half-filling. Away from the particle–hole symmetric point the c-SF phase is always spontaneously magnetized, leading to the formation of different c-SF domains in systems where the total number of particles of each species is conserved. This can be seen as the SU(3) symmetric realization of a more general tendency for phase separation in three-component Fermi mixtures. The three-body constraint strongly disfavors the trionic phase, stabilizing a (fully magnetized) c-SF also at strong coupling. With increasing temperature we observe a transition to a non-magnetized SU(3) Fermi liquid phase.
Highlights
Multi-species Hubbard models have attracted considerable interest on the theoretical side in recent years
By using a generalized BCS approach [17]–[19], it was shown that the ground state at weak coupling spontaneously breaks the SU(3) ⊗ U(1) symmetry down to SU(2) ⊗ U(1), giving rise to a color superfluid (c-SF) phase, where superfluid pairs coexist with unpaired fermions
We proved that the c-SF phase close to Uc2 is metastable with respect to the t-CDW phase and the existence of the threshold could result from an inability of our dynamical mean-field theory (DMFT) solver to further follow the metastable c-SF phase at strong coupling
Summary
Three-component Fermi mixtures with attractive two-body interactions loaded into an optical lattice are well described by the following Hamiltonian:. In this case, Hamiltonian (1) reduces to an SU(3) attractive Hubbard model if V = 0. Whenever the SU(3) symmetry is explicitly broken, only the pairing between the natural species is allowed to comply with the Ward–Takahashi identities [37] This reduces the continuum set of equivalent pairing channels of the symmetric model to a discrete set of three (mutually exclusive) options for pairing, i.e. 1–2, 1–3 or 2–3. In this case, the natural choice would be that pairing takes place in the channel corresponding to the strongest coupling when the mixture is globally balanced. The formalism developed here is fully general and includes both the symmetric and non-symmetric cases, while only in the SU(3)-symmetric case our approach corresponds to a specific choice of the gauge
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