Abstract
We show that a linear term coupling the atoms of an ultracold binary mixture provides a simple method to induce an effective and tunable population imbalance between them. This term is easily realized by Rabi coupling between different hyperfine levels of the same atomic species. The resulting effective imbalance holds for one-particle states dressed by the Rabi coupling and obtained by diagonalizing the mixing matrix of the Rabi term. This way of controlling the chemical potentials applies to both bosonic and fermionic atoms and it also allows for spatially- and temporally-dependent imbalances. As a first application, we show that, in the case of two attractive fermionic hyperfine levels with equal chemical potentials coupled by the Rabi pulse, the same superfluid properties of an imbalanced binary mixture are recovered. We finally discuss the properties of m-species mixtures in the presence of SU(m)-invariant interactions.
Highlights
The average density of particles is a central parameter in ultracold experiments [1,2], and in general for condensed matter phenomena
We provide a different method to induce and to control effective population imbalances in experiments involving atoms of a binary mixture linearly coupled between them, a major example being different hyperfine levels populated coupled by a Rabi rf-field
The discussion above suggests that our method provides a new method for efficiently probing the physics of interacting imbalanced mixtures
Summary
The average density of particles is a central parameter in ultracold experiments [1,2], and in general for condensed matter phenomena. Designing alternative methods to tune imbalances effectively appears a very interesting task This can be even more relevant if the chemical potential can be tuned in a space- or time-dependent way, which is not easy to realize controlling the atomic populations. We focus on an attractive two-species fermionic mixture, showing that its superfluid properties under Rabi coupling are the same as those of an imbalanced mixture in the absence of a Rabi term This example is interesting in view of the rich phenomenology of the imbalanced Fermi gases as imbalance and interaction vary, including FFLO physics (see e.g., [4,5] and references therein).
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