Phase diagrams of the S= quantum antiferromagnetic XY model on the triangular lattice in magnetic fields

摘要: We study the S=1/2 quantum antiferromagnetic XY model on finite triangular lattices with N sites in both longitudinal and transverse magnetic fields. calculate physical quantities ground state using a diagonalization for spins $N \leq 27$, those at temperatures transfer Monte Carlo method 24$. In field, long-range chiral order parameter seems to have finite, nonzero value low suggesting occurrence of classical umbrella-type phase. 1/3-plateau magnetization curve appears even temperatures, contrast model. The field dependences parameters suggest that chiral-ordered, ferrimagnetic, spin flop phases appear successively as is increased. transition are estimated from peak position specific heat, phase diagrams predicted