Phase transitions of the frustrated bilayer spin one XY model

Antonio S. T. Pires

Antonio S. T. Pires

Colin Denniston B, Chao Tang

Anderson Barbosa Lima, B. V. Costa

Antonio S. T. Pires

Abstract The spin-one honeycomb bilayer XY antiferromagnet has been studied taking into account the effect of the next-near neighbor J2 exchange interactions and single-ion easy plane anisotropy, using a flavor wave theory. We found that, at a critical point α C = 13.8 , where α = J ⊥ / J 1 is the ratio between the interlayer J ⊥ to the intralayer near neighbor J1 exchange interaction, the system shows a quantum phase transition from an Neel ordered phase to a paramagnetic phase. The phase diagram at zero temperature is presented.

Petter Minnhagen, Sebastian Bernhardsson, Beom Jun Kim

The 2D Fully Frustrated XY(FFXY) class of models is shown to contain a new groundstate in addition to the checkerboard groundstate of the standard 2D XY model. The spin configuration of this additional groundstate is obtained and its connection to a broken Z2-symmetry explained. This means that the class of 2D FFXY models belongs within a U(1) ⊗ Z2 ⊗ Z2-symmetry phase-transition representation. The phase diagram is reviewed and the central charges of the four multicritical points described. The implications for the standard 2D FFXY-model are discussed and elucidated, in particular with respect to the long standing controversy concerning the phase transitions of the standard 2D FFXY-model.