Multicritical point of an S = 1 XXZ chain with single-ion anisotropy

We research the ground state of the $S=1$ XXZ spin chain with single-ion anisotropy, focusing on XY1, XY2 (spin nematic), N\'eel, and Haldane phases. Recently, it was reported that the four phases did not intersect at a single point using conventional numerical methods, which is inconsistent with the bosonization theory. In order to resolve this discrepancy, we propose a unified method to determine phase boundaries by combining conformal field theory with numerical diagonalization. In addition, we discuss the symmetry and universality class of the multicritical point.