A BCS Gap on the Lattice

Monte Carlo simulations of the 3+1 dimensional NJL model are performed with baryon chemical potential μ > 0. For μ ∼ Σ0, the constituent quark mass in vacuum, chiral symmetry is restored and a diquark condensate 〈qq+〉 forms. We analyse the fermion propagator and find evidence for particle-hole mixing in the vicinity of the Fermi surface and an energy gap ∆ > 0, both of which provide evidence for superfluidity at high baryon density induced by a BCS mechanism. At μa = 0.8 the ratio between the BCS gap and the vacuum quark mass is ∆/Σ0 = 0.15(2).