QCD phase diagram at finite baryon and isospin chemical potentials

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 root sigma(2) + pi(2) defined by the chiral and pion condensates, sigma and pi.