At zero temperature and finite chemical potential, the gap equation of cold dense quark matter under external magnetic field is studied with NJL model in the mean-field approximation. By introducing new methods, it is found that the Nambu phase has sophisticated structures which have not been studied before. As a consequence, the phase diagram is expanded and divided into five areas, in each area the condensate has unique behaviors with chemical potential varying. Furthermore, the expanded phase diagram is used to predict the order of phase transition between the Nambu phase and the Wigner phase, it can also be used to explain the relations of dynamical mass and chemical potential. Meanwhile, the metastable states and cascade effect of dynamical mass are studied in this paper.
Pions in the quark matter phase diagram