High-Temperature Atomic Superfluidity in Lattice Boson-Fermion Mixtures

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We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always attractive if the boson-boson on site interaction is repulsive, and predict the existence of an enhanced BEC--BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion repulsion, the induced attraction can give rise to superfluidity via s-wave pairing, at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions.