  Repulsive Bose-Bose mixtures are known to either mix or phase-separate into
pure components. Here we predict a mixed-bubble regime in which bubbles of the
mixed phase coexist with a pure phase of one of the components. This is a
beyond-mean-field effect which occurs for unequal masses or unequal
intraspecies coupling constants and is due to a competition between the
mean-field term, quadratic in densities, and a nonquadratic beyond-mean-field
correction. We find parameters of the mixed-bubble regime in all dimensions and
discuss implications for current experiments.
