Phase diagram and quasiparticles of a lattice SU(2) scalar-fermion model in 2+1 dimensions -: art. no. 034501

The phase diagram at zero temperature of a lattice SU(2) scalar-fermion model in 2+1 dimensions is studied numerically and with mean-field methods. Special attention is devoted to the strong coupling regime. We have developed a new method to adapt the hybrid Monte Carlo algorithm to the O(3) non-linear sigma model constraint. The charged excitations in the various phases are studied at the mean field level. Bound states of two charged fermions are found in a strongly coupled paramagnetic phase. On the other hand, in the strongly coupled antiferromagnetic phase fermionic excitations around momenta (+/- pi/2,+/-pi/2,+/-pi/2) emerge.