Phase transition in two-flavor dense QCD from the Schwinger-Dyson equation

We investigate the phase structure of the two-flavor dense QCD using the SchwingerDyson equation (SDE) with the improved ladder approximation in the Landau gauge. The SDE for diquark condensate (color superconducting condensate) and that for quarkantiquark condensate (chiral condensate) are solved separately. In the low density region both the SDE’s have nontrivial solutions which correspond to the color symmetry breaking (CSB) vacuum and the chiral symmetry breaking (χSB) vacuum. Comparing the values of the effective potential at two vacua, we show that the χSB vacuum is more stable than the CSB vacuum in the low density region, and that the phase transition from the χSB vacuum to the CSB vacuum is of first order. The critical value of the chemical potential at the phase transition point is found to be smaller than that obtained by the SDE-analysis with including only the chiral condensate.