Finite-temperature pairing gap of a unitary fermi gas by quantum monte carlo calculations.

We calculate the one-body temperature Green's (Matsubara) function of the unitary Fermi gas via quantum Monte Carlo, and extract the spectral weight function A(p,omega) using the methods of maximum entropy and singular value decomposition. From A(p,omega) we determine the quasiparticle spectrum, which can be accurately parametrized by three functions of temperature: an effective mass m{*}, a mean-field potential U, and a gap Delta. Below the critical temperature T{c}=0.15 epsilon{F} the results for m{*}, U, and Delta can be accurately reproduced using an independent quasiparticle model. We find evidence of a pseudogap in the fermionic excitation spectrum for temperatures up to T{*} approximately 0.20 epsilon{F}> T{c}.