Zeroth-order phase transition in the Blume-Emery-Griffiths model without bilinear exchange coupling

We study the simplified Blume-Emery-Griffiths model without bilinear exchange coupling both in the microcanonical ensemble and in the canonical ensemble. This model can exhibit a zeroth-order phase transition in the microcanonical ensemble accompanied by a finite entropy jump. However, this singularity in entropy cannot be observed in the canonical ensemble, which illustrates the ensemble inequivalence. Moreover, the global phase diagram of this model is given in both ensembles.

Automated summary

In this study, we focused on the simplified Blume-Emery-Griffiths model without bilinear exchange coupling in both the microcanonical and the canonical ensemble. The model displayed a zeroth-order phase transition and finite entropy jump in the microcanonical ensemble, while this singularity in entropy was not observed in the canonical ensemble, illustrating ensemble inequivalence. The global phase diagram of the model was also provided in both ensembles.