One-loop effective potential for two-dimensional competing scalar order parameters

Abstract

Using the method of the effective potential of quantum field theory, we compute the quantum corrections to the phase diagram of systems with competing order parameters. This is specially useful to study metallic systems with competing antiferromagnetic and superconducting ground states. We focus on the two-dimensional (2d) case that is relevant for high Tc superconductors and heavy fermion systems. We consider two different types of couplings between the order parameters and obtain the modifications in the phase diagrams due to critical quantum fluctuations in these systems with conflicting orders. We consider z = 1, as well as, a dissipative z = 2 dynamics, typical of antiferromagnetic metals close to the magnetic quantum critical point. Our results, when compared to those in the 3d case, show that these depend strongly on both dimensionality and dynamics of the propagators describing the excitations of the possible ordered states. We find stable unconventional coexisting phases, as well as, the enhancement of the region of coexistence by fluctuations. These effects may be observed experimentally in many interesting cases of strongly correlated materials.