Coulomb interaction effects in a two-dimensional quantum well with spin-orbit interaction

Starting from general total-energy considerations, we demonstrate that the SU(2) spin-rotation symmetry and the resulting persistent helical state (PHS) predicted to occur in an electron system with equal Rashba-Dresselhaus coupling constants are not in fact realized. On account of the accidental degeneracy that appears in the single-particle spectrum, the Coulomb interaction favors the apparition of an itinerant antiferromagnetic (IAF) order characterized by a fractional polarization of fixed spatial orientation. Within the Hartree-Fock approximation, we obtain numerical results that describe the temperature evolution of the order parameter in the IAF state and determine the critical temperature of the transition to the paramagnetic state.