The self-consistent mean field approximation of the two-flavor NJL model, with a free parameter to reflect the competition between the "direct" channel and the "exchange" channel, is employed to study the QCD phase structure at finite isospin chemical potential , finite baryon chemical potential and finite temperature T, and especially to study the location of the QCD critical point. Our results show that in order to match the corresponding lattice results of isospin density and energy density, the contributions of the "exchange" channel need to be considered in the framework of the NJL model, and a weighting factor should be taken. It is also found that for fixed isospin chemical potentials, the lower temperature of the phase transition is obtained with increasing in the plane, and the largest difference of the phase transition temperature with different 's appears at . At the temperature of the QCD critical end point (CEP) decreases with increasing , while the critical baryon chemical potential increases. At high isospin chemical potential ( MeV), the temperature of the QCD tricritical point (TCP) increases with increasing , and in the low temperature regions the system will transition from the pion superfluidity phase to the normal phase as increases. At low density, the critical temperature of the QCD phase transition with different 's rapidly increases with at the beginning, and then increases smoothly around MeV. In the high baryon density region, the increase of the isospin chemical potential will raise the critical baryon chemical potential of the phase transition.

两种风味 NJL 模型的自洽平均场近似，具有反映“直接”通道和“交换”通道之间竞争的自由参数，用于研究有限同位旋化学势下的 QCD 相结构，有限重子化学势和有限温度T，特别是研究 QCD 临界点的位置。我们的结果表明，为了匹配同位旋密度和能量密度的相应晶格结果，需要在 NJL 模型的框架中考虑“交换”通道的贡献，以及一个加权因子应采取。还发现，对于固定的同位旋化学势，随着平面内的增加，相变温度较低，不同的相变温度的最大差异出现在。在温度 QCD 的临界终点（CEP）随着 的增加而降低，而临界重子化学势增加。在高同位旋化学势 ( MeV) 下，QCD 三临界点 (TCP) 的温度随着 的增加而增加，在低温区域系统将从 pion 超流态转变为正相，如增加。在低密度下，QCD 相变的临界温度随着开始迅速升高，然后在MeV附近平稳升高。在高重子密度区域，同位旋化学势的增加将提高相变的临界重子化学势。