Critical properties of xy spin-one chains with uniaxial single-ion anisotropy

We use finite-size methods to estimate the critical properties of s=1 xy chains with uniaxial single-ion anisotropy of strength D. Strong evidence is presented for a phase transition, belonging to the universality class of the 1D quantum 0(2) model, with the weak coupling phase gapless, an essential zero in the gap at the critical coupling D*, and critical exponents z(D*)≊1, η(D*)≊1/4. Like the quantum 0(2) system, one of the models turns out to be a 1D quantum analog of the classical and isotropic 2D xy model.