title: Collective pairing of resonantly coupled microcavity polaritons.
abstract: We consider the possible phases of microcavity polaritons tuned near a bipolariton Feshbach resonance. We show that, as well as the regular polariton superfluid phase, a "molecular" superfluid exists, with (quasi-)long-range order only for pairs of polaritons. We describe the experimental signatures of this state. Using variational approaches we find the phase diagram (critical temperature, density, and exciton-photon detuning). Unlike for ultracold atoms, the molecular superfluid is not inherently unstable, and our phase diagram suggests it is attainable in current experiments.
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid 28049, Spain.
authors.forename: F M
authors.initials: FM
authors.lastname: Marchetti
authors.affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Keeling