  In this paper, we aim to study the complete self-energy in the fermion
propagator within two-flavor NJL model in the case of finite temperature,
chemical potential and external magnetic field. Through Fierz transformation we
prove that the self-energy is not simply proportional to dynamical mass in the
presence of chemical potential, moreover, it contains four kinds of condensates
after introducing external magnetic field. We find out the appropriate and
complete form of self-energy and establish new gap equations. We take two of
the four condensates (scalar and pseudovector condensates) to make an
approximation and simplify the gap equations. The numerical results show that
not only the dynamical mass get quantitative modification, but also the
properties of Nambu phase and Wigner phase are significantly different with
classic results. Instead of classic Wigner phase with zero dynamic mass in the
massless NJL model, we propose a new phase - quasi-Wigner phase in this
article, it has small but nonzero dynamic mass, with increasing chemical
potential, eventually Nambu phase will turn into quasi-Wigner phase with
first-order phase transition, therefore the chiral symmetry can never be fully
restored but be partially restored. Furthermore, we prove that pseudovector
condensate in self-energy can generate energy splitting in dispersion relation,
it will cause minor differences of particle numbers with the split energy
levels.
