Spin-imbalanced pairing and Fermi surface deformation in flat bands

摘要: We study the attractive Hubbard model with spin imbalance on two lattices featuring a flat band: Lieb and kagome lattices. present mean-field phase diagrams exotic superfluid phases, similar to Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, whose stability is confirmed by dynamical theory. The nature of pairing found be richer than just Fermi surface shift responsible for usual FFLO state. presence band allows changes in particle momentum distributions at null energy cost. This facilitates formation nontrivial phases via multiband Cooper pair formation: distribution component deforms mimic other residing dispersive band. unpaired particles that are typical gapless superfluids becomes deformed as well. results highlight profound effect dispersions instabilities, provide potential route observing spin-imbalanced superfluidity superconductivity.