The (2+1)-dimensional Gross–Neveu model with a U(1) chiral symmetry at nonzero temperature

We present results from numerical simulations of the (2+1)-dimensional Gross–Neveu model with a U(1) chiral symmetry and Nf=4 fermion species at nonzero temperature. We provide evidence that there are two different chirally symmetric phases, one critical and one with finite correlation length, separated by a Berezinskii–Kosterlitz–Thouless transition. We have also identified a regime above the critical temperature in which the fermions acquire a screening mass even in the absence of chiral symmetry breaking, analogous to the pseudogap behaviour observed in cuprate superconductors.