Zeros of the partition function for the two-dimensional Z5-symmetric spin model.

Abstract

We have numerically computed the exact distribution of zeros of the partition function for the ${\mathit{Z}}_{5}$-symmetric spin model on square lattices of linear size 3\ensuremath{\le}L\ensuremath{\le}7. At a point of the phase diagram close to the clock-model point, we observe two distinct lines of zeros, which converge towards two well-separated points of the real axis as L increases, thereby clearly signaling the existence of two phase transitions and confirming the emergence of the expected soft phase.