The phase structure of two-flavor QCD is explored for thermal systems with finite baryon- and isospin-chemical potentials, mu_B and mu_{ iso}, by using the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. The PNJL model with the scalar-type eight-quark interaction can reproduce lattice QCD data at not only mu_{ iso}=mu_B=0 but also mu_{ iso}>0 and mu_B=0. In the mu_{ iso}-mu_{ B}-T space, where T is temperature, the critical endpoint of the chiral phase transition in the mu_B-T plane at mu_{ iso}=0 moves to the tricritical point of the pion-superfluidity phase transition in the mu_{ iso}-T plane at mu_B=0 as mu_{ iso} increases. The thermodynamics at small T is controlled by sqrt{ sigma^2+pi^2} defined by the chiral and pion condensates, sigma and pi.
Categories: hep-ph hep-lat hep-th nucl-th