Nonuniversal equation of state for Rabi-coupled bosonic gases: a droplet phase

Abstract: Through an effective quantum field theory including zero temperature Gaussian fluctuations we derive analytical and explicit expressions for the equation of state of three-dimensional ultracold Rabi-coupled two-component bosonic gases with nonuniversal corrections to the interactions. At mean-field level the system presents two ground-states, one symmetric and one non-symmetric or unbalanced. For the symmetric ground state, in the regime where inter-species interactions are weakly attractive and subtly higher than repulsive intra-species, the instability by collapse is avoided by the contribution arising from Gaussian fluctuations, driving thus to formation of a liquidlike phase or droplet phase. This self-bound state is crucially affected by the dependence on the nonuniversal corrections to the interactions, which acts controlling the droplet stability. By tuning the ratio between the inter-species scattering length and the intra-species scattering lengths or the nonuniversal contribution to the interactions we address and establish conditions under which the formation and stability of self-bound Rabi-coupled droplets with nonuniversal corrections to the interactions is favorable.