Communal pairing in spin-imbalanced Fermi gases

A spin-imbalanced Fermi gas with an attractive contact interaction forms a superconducting state whose underlying components are superpositions of Cooper pairs that share minority-spin fermions. This superconducting state includes correlations between all available fermions, making it energetically favorable to the Fulde-Ferrell-Larkin-Ovchinnikov superconducting state. The ratio of the number of up-and down-spin fermions in the instability is set by the ratio of the up-and down-spin density of states in momentum at the Fermi surfaces, to fully utilize the accessible fermions. We present analytical and complementary Diffusion Monte Carlo results for the state. Copyright (C) EPLA, 2019